The Ultimate Cheesy Collard Greens Gratin: A Southern Comfort Masterpiece

There are side dishes, and then there are legendary side dishes the ones that steal the show, often eclipsing the main course entirely. In the realm of elevated comfort food, few recipes achieve the perfect balance of texture, flavor, and richness quite like a magnificent gratin. Today, we are bridging the gap between classic Southern cooking and sophisticated French technique with our recipe for Cheesy Collard Greens Gratin. This is not your grandmother’s traditional pot of boiled greens; this is a luxurious, creamy, and smoky casserole crowned with a golden, crunchy Panko crust.

If you thought collard greens were too tough, too bitter, or destined only for long hours of boiling with ham hocks, prepare to have your mind changed. This recipe transforms the humble collard into a decadent, velvety side dish. We start by braising the greens until they are melt-in-your-mouth tender, using smoky bacon and a splash of tangy vinegar to cut through the richness. Then, we fold them into a silken, three-cheese béchamel sauce featuring sharp cheddar, nutty Gruyère, and a secret touch of cream cheese for unparalleled smoothness.

Perfect for holiday tables, Sunday dinners, or anytime you crave serious comfort, this Cheesy Collard Greens Gratin offers complex flavor in every forkful. The key to success lies in two steps: thoroughly braising the greens and, critically, draining them completely before adding the cheese sauce. Follow our detailed instructions, and you will achieve a bubbly, deeply satisfying casserole that will quickly become a cherished favorite.

Why You’ll Fall Head Over Heels for This Cheesy Collard Greens Gratin

This dish is more than just a casserole; it’s an experience in contrasting flavors and textures, meticulously engineered for maximum appeal. When crafting a rich side dish like a gratin, the goal is to balance the heavy creaminess with something bright or earthy. Collard greens, with their inherent earthiness and slight bitterness, are the ideal counterpoint to a rich cheese sauce. Here is exactly why this specific recipe for Cheesy Collard Greens Gratin deserves a permanent spot in your rotation.

The Perfect Texture Contrast

Many creamed side dishes suffer from being uniformly soft. This Cheesy Collard Greens Gratin is built on a tripartite textural foundation that keeps every bite interesting:

• The Tender Greens: Braised low and slow, the collards become incredibly soft and silky, maintaining their shape without being chewy.
• The Velvety Sauce: Thanks to the inclusion of both Gruyère and cream cheese in the béchamel, the sauce is exceptionally smooth and coats the greens beautifully, rather than becoming a grainy mess.
• The Crispy Topping: The Panko and Parmesan topping bakes up into a brilliant, golden-brown shield. This crunch provides a vital textural contrast that elevates the entire dish from a simple baked side to a true gratin.

Deep and Complex Flavor Layers

Flavor is built in stages in this recipe, moving far beyond simple cheese and vegetables:

1. Smoky Base: We start by rendering thick-cut bacon, which infuses the oil with a deep, savory smokiness. This fat is then used to sauté the onions and garlic, carrying that foundational flavor into the greens as they braise.
2. Acidity for Balance: The addition of Apple Cider Vinegar is critical. Collard greens can handle, and indeed require, a touch of acid to balance their robust flavor. The vinegar brightens the greens and prevents the final dish from tasting too heavy or one-dimensional.
3. Rich Umami: The three-cheese blend (Sharp White Cheddar, Gruyère, and Parmesan in the topping) provides layered umami complexity. The Sharp Cheddar offers a familiar tang, while the Gruyère melts beautifully and provides a nutty, earthy depth often associated with higher-end gratins.

This careful layering ensures that the final product is not merely cheesy, but genuinely flavorful and deeply satisfying, offering a complexity that rivals even the finest mac and cheese. It elevates the classic Southern green into an elegant presentation perfect for any special occasion. If you enjoy classic comfort food with an upscale flair, this gratin offers the perfect opportunity to impress your guests, much like mastering other beloved side dishes such as Easy Garlic Mashed Potatoes, only with an intriguing, verdant twist.

Beyond the Basics: Why You Must Try This Cheesy Collard Greens Gratin Recipe Today

In the culinary world, collard greens have long been associated with long, slow cooking times necessary to break down their robust structure. While many traditional recipes sacrifice color and nutrients for tenderness, this modern approach ensures tender greens enveloped in a creamy matrix, without turning them into mush. This recipe is a must-try because it specifically addresses and solves the three main challenges associated with making creamed greens: texture, bitterness, and liquid content.

Solving the Watery Gratin Dilemma

The number one mistake when making any creamed vegetable casserole is insufficient draining, which results in a watery, soupy final product where the cheese sauce separates. Collard greens, like spinach, release significant moisture as they braise. Our instructions emphasize a thorough, firm draining step (using a large colander and pressing down) that is absolutely non-negotiable. Getting the greens as dry as possible is the single most important technique for achieving a perfectly firm, creamy, and sliceable Cheesy Collard Greens Gratin.

The Art of Braising for Flavor and Tenderness

We skip the quick steam or boil and opt for a true braise. By cooking the collards for 45 minutes to an hour in stock and bacon fat, they absorb moisture and flavor deep into their fibers. This long, gentle simmer softens the cell walls, transforming the tough leaves into velvety tenderness. The braising liquid, enriched with stock and the tang of apple cider vinegar, ensures the final taste is balanced and savory, not overwhelmingly vegetal or harsh.

An Elevated Cheese Experience

While standard creamed greens might rely solely on Cheddar, this recipe upgrades the sauce using a sophisticated blend. Gruyère is renowned for its excellent melting properties and deep, earthy flavor that pairs exceptionally well with brassicas like collards. The addition of softened cream cheese acts as an emulsifier, guaranteeing a silky-smooth béchamel that resists breaking or becoming grainy, even under high heat. This three-cheese combination ensures maximum flavor delivery throughout every spoonful of the creamy collard gratin.

Furthermore, this recipe offers incredible versatility, making it suitable for both a weeknight family meal and a holiday feast. Imagine serving this alongside your Thanksgiving turkey or Christmas ham it’s a comforting, unexpected green that offers the warmth and familiarity of classics like Jiffy Corn Casserole, but with a refined Southern twist. By following this tried-and-tested method, you are guaranteed a professional-quality gratin that avoids all the typical pitfalls.

Mastering the Ingredients and Essential Kitchen Tools for the Perfect Cheesy Collard Greens Gratin

The success of this Cheesy Collard Greens Gratin relies on sourcing quality ingredients and having the right tools prepared. Below is a detailed breakdown of the components and the necessary kitchen arsenal, ensuring you are fully equipped before you begin.

Required Ingredients with Pro Tips

The list is divided into three distinct sections, mirroring the preparation process:

For the Collard Greens

• 2 large bunches of fresh Collard Greens (about 2.5 to 3 lbs): Crucial Prep: Remove the tough, thick central stems before coarsely chopping. The stems will not tenderize sufficiently and will distract from the texture of the final dish.
• 4 cups Low-Sodium Chicken or Vegetable Stock: Using low-sodium stock allows you to control the final seasoning, especially since bacon and cheese are already salty.
• 4 slices of thick-cut Bacon, diced: We use thick-cut bacon primarily for the high quality rendered fat (schmaltz). This fat is indispensable for flavoring the aromatics before braising. If omitting bacon for vegetarian reasons, substitute 2 tablespoons of olive oil or butter, but understand the smoky depth will be diminished.
• 1 medium Yellow Onion, finely diced: The foundation of flavor when sautéed in bacon fat.
• 3 cloves Garlic, minced: Adds necessary pungent warmth.
• 1 teaspoon Red Pepper Flakes (optional): Highly recommended. Collards pair beautifully with heat, which also helps cut through the richness of the cheese.
• 2 tablespoons Apple Cider Vinegar: Non-negotiable for balance. This acidity tames any lingering bitterness in the greens and brightens the overall flavor profile.
• Salt and freshly ground Black Pepper, to taste: Seasoning should be reserved until after the greens are drained and mixed with the sauce, as the stock, bacon, and cheese all contribute salt.

For the Rich Cheese Sauce (Béchamel Base)

The béchamel is the heart of the Cheesy Collard Greens Gratin. Precision in this section ensures a silky, lump-free result.

• 4 tablespoons Unsalted Butter: Used for the roux base. Unsalted butter gives you control over salinity.
• 1/4 cup All-Purpose Flour: Combined with the butter to create the roux, which is essential for thickening the sauce. Cook the roux for at least two minutes to eliminate the raw flour taste.
• 3 cups Whole Milk or Half-and-Half, warmed slightly: Tip: Warming the milk slightly prevents the sauce from cooling down rapidly when added to the roux, reducing the chance of lumps forming. Whole milk provides adequate richness; Half-and-Half makes it truly decadent.
• 1/2 teaspoon freshly grated Nutmeg: Nutmeg is the classic, essential seasoning for béchamel-based sauces, especially when combined with Gruyère. It adds warmth and aromatic complexity.
• 8 ounces Sharp White Cheddar Cheese, shredded: Provides the strong, sharp flavor profile. Buy a block and shred it yourself; pre-shredded cheese contains starches that can make the sauce slightly grainy.
• 4 ounces Gruyère Cheese, shredded: Key for superior melting and a sophisticated, nutty flavor. It melts beautifully and adds a refined taste to the creamy collard gratin.
• 2 ounces Cream Cheese, softened and cubed: The secret weapon. Cream cheese ensures the final sauce is incredibly smooth and velvety, providing stability and richness that prevents separation.
• 1 teaspoon Kosher Salt and 1/2 teaspoon Black Pepper: Seasoning for the sauce base.

For the Topping

• 1 cup Panko Breadcrumbs: Panko (Japanese-style breadcrumbs) are larger and absorb less oil than traditional breadcrumbs, resulting in a much crispier, lighter crust.
• 3 tablespoons Unsalted Butter, melted: To bind the Panko and help it brown evenly.
• 1/4 cup grated Parmesan Cheese: Adds a salty, crunchy, savory boost to the crust.

Essential Utensils and Equipment

While many home cooks already possess these items, having the right tools streamlines the preparation of this Cheesy Collard Greens Gratin:

1. Large Dutch Oven or Stockpot (6-8 quarts): Necessary for braising the large volume of collard greens. They shrink significantly, but initially require ample space.
2. 9×13 inch Baking Dish (3-quart capacity): The standard size for gratins and casseroles. Ensure it is lightly greased.
3. Large Colander: Absolutely critical for draining the collard greens thoroughly after braising.
4. Medium Saucepan: Used exclusively for preparing the béchamel sauce.
5. Whisk and Rubber Spatula: A whisk is essential for making a smooth, lump-free roux and béchamel. The spatula is great for folding the greens into the thick sauce.
6. Sharp Chef’s Knife and Cutting Board: For prepping the collards, bacon, and onions.

If you are looking for more tips and visual guides on preparing fantastic holiday side dishes and mastering your cooking techniques, be sure to check out my collection of recipes and culinary tips on Pinterest: Recipes Luna Blog on Pinterest.

Step-by-Step Guide: How to Assemble the Ultimate Cheesy Collard Greens Gratin

Creating this magnificent casserole involves three main stages: braising the greens, preparing the cheese sauce, and assembly. Precision in the first two stages is key to avoiding a watery gratin.

Part 1: Preparing and Cooking the Collard Greens

This stage ensures the greens are perfectly tender, deeply flavored, and free of excess moisture.

1. Prep the Oven and Baking Dish: Preheat your oven to 375°F (190°C). Lightly grease a 9×13 inch (or similarly sized 3-quart) baking dish.
2. Render the Bacon (Flavor Base): In a large Dutch oven or stockpot, render the diced bacon over medium heat until crispy. Use a slotted spoon to remove the bacon bits and transfer them to a paper-towel-lined plate. Set the crispy bacon aside for later use in the final assembly. Leave the flavorful bacon fat (schmaltz) in the pot.
3. Sauté Aromatics: Add the finely diced yellow onion to the hot bacon fat. Sauté for 5 to 7 minutes until the onion is soft, translucent, and slightly sweet. Add the minced garlic and red pepper flakes (if using). Cook for just 1 minute more, stirring constantly, until the garlic is fragrant. Be careful not to burn the garlic.
4. Cook the Collards: Add the large volume of chopped collard greens to the pot. Initially, they will pile high, but they will wilt quickly. Cook the greens for about 5 minutes, stirring often, allowing them to shrink significantly and begin to collapse.
5. Braise: Pour in the 4 cups of chicken or vegetable stock and the 2 tablespoons of apple cider vinegar. Bring the mixture just to a simmer. Once simmering, immediately cover the pot and reduce the heat to very low. Let the greens braise for a lengthy period 45 minutes to 1 hour or until they are exceptionally tender and easy to cut with a spoon.
6. Drain Thoroughly (The Most Important Step): This step is non-negotiable for a creamy gratin. Drain the cooked collards completely using a large colander. Press down firmly and repeatedly with the back of a large spoon or ladle to squeeze out as much liquid as possible. The drier the greens, the creamier your final Cheesy Collard Greens Gratin will be. Set the drained, pressed greens aside in a large mixing bowl.

Part 2: Making the Béchamel Cheese Sauce (Mornay)

This is the quick stage that delivers the luscious, creamy texture.

1. Make the Roux: In a medium saucepan, melt the 4 tablespoons of butter over medium heat. Once melted and bubbly, whisk in the flour. Cook the mixture, stirring constantly, for 2 minutes. This cooking time is essential to cook out the raw, pasty taste of the flour. This is your roux base.
2. Add Milk Gradually: Reduce the heat slightly. Gradually whisk in the warm milk (or half-and-half), adding about a cup at a time. Whisk vigorously and continuously, ensuring all lumps are completely dissolved before incorporating the next addition. Continue whisking as the sauce heats and thickens. This usually takes about 8 to 10 minutes. The sauce is ready when it is thick enough to evenly coat the back of a wooden spoon.
3. Season and Add Cheese: Remove the saucepan from the heat immediately after it thickens. Stir in the Kosher salt, black pepper, and the crucial freshly grated nutmeg. Add the shredded sharp cheddar, Gruyère, and the cubed, softened cream cheese. Stir gently but continuously until all the cheese has melted completely and the sauce is perfectly smooth, creamy, and velvety. Do not return the sauce to boiling once the cheese is added, as this can cause separation.

Part 3: Assembly and Baking

Bringing all the components together for the golden finish.

1. Combine: Pour the finished cheese sauce directly over the thoroughly drained collard greens in the large mixing bowl. Add the reserved crispy bacon bits (if using). Gently toss the mixture until the collards are thoroughly and evenly coated with the thick sauce. This mixture should look creamy and dense, not soupy.
2. Transfer to Dish: Pour the collard green and cheese mixture into the prepared 9×13 inch baking dish, spreading it into an even layer using the back of a spoon or spatula. Ensure it is distributed evenly for consistent cooking.
3. Prepare Topping: In a small separate bowl, combine the Panko breadcrumbs, 3 tablespoons of melted butter, and the grated Parmesan cheese. Toss everything together until the Panko is uniformly coated in the butter mixture.
4. Bake: Sprinkle the buttery Panko and Parmesan topping evenly over the collard greens mixture.
5. Final Bake: Bake for 25 to 30 minutes in the preheated 375°F (190°C) oven. The Cheesy Collard Greens Gratin is done when the sauce is actively bubbling around the edges (indicating it’s hot throughout) and the breadcrumb topping is gorgeously golden brown and crisp.
6. Rest and Serve: Allow the gratin to rest on the counter for 10 minutes before slicing and serving. This resting period is essential as it gives the sauce time to cool slightly and fully set, ensuring clean, beautiful servings. This step is equally vital for other comfort casseroles like Green Bean Casserole with Cream Cheese.

Tips, Troubleshooting, and Delicious Variations for Your Collard Greens Gratin

Making a successful gratin is easy once you understand the basic science behind the cheese sauce and liquid content. Here are some essential tips, common troubleshooting advice, and creative variations to personalize your Cheesy Collard Greens Gratin.

Troubleshooting Common Gratin Mistakes

Issue 1: The Gratin is Watery

This is almost always due to insufficient draining of the collard greens. After braising, collards retain a surprising amount of liquid. You must press them firmly in the colander. If you still find your finished gratin a little loose, try this next time: after draining, spread the greens out on a baking sheet lined with paper towels and let them air dry for 10-15 minutes before mixing with the sauce.

Issue 2: The Cheese Sauce is Grainy or Separated

Graininess can occur for a few reasons:

• Boiling the Cheese: If you add the shredded cheese while the béchamel is still simmering or boiling, the milk proteins can seize up, resulting in a grainy texture. Always remove the saucepan from the heat before adding the cheese.
• Pre-Shredded Cheese: Pre-shredded cheese contains anti-caking agents (like potato starch or cellulose) that prevent it from melting smoothly. Shredding cheese fresh from the block yields the creamiest results.

Issue 3: The Topping Burned Too Quickly

If your oven runs hot, or if the topping is browning before the interior is fully bubbly, cover the gratin loosely with aluminum foil for the first 15-20 minutes of baking, then remove the foil for the last 10 minutes to allow the Panko to crisp and brown.

Delicious Variations to Try

Vegetarian/Meatless Option

Easily make this a show-stopping vegetarian side dish. Omit the bacon entirely. Instead of using bacon fat for the aromatics, use 2 tablespoons of olive oil or butter. Consider adding a pinch of smoked paprika or a teaspoon of liquid smoke to the braising liquid to replicate a savory, smoky depth.

Gluten-Free Variation

Swap the all-purpose flour for a cup-for-cup gluten-free flour blend when making the roux. For the topping, ensure you use gluten-free Panko breadcrumbs (easily found in most major grocery stores) or crushed pork rinds (for a keto-friendly, crunchy, savory alternative).

Cheese Blend Alternatives

While the Sharp Cheddar and Gruyère blend is divine, you can experiment:

• Spicier Kick: Use Pepper Jack or a strong Monterey Jack in place of the Sharp Cheddar.
• Stronger Southern Flavor: Substitute the Gruyère for Smoked Gouda or Muenster cheese.
• Richer Flavor: Replace the Sharp Cheddar with an Aged White Cheddar for an intense, pungent profile.

Adding Extra Vegetables

For a heartier casserole, consider folding in other ingredients along with the greens, such as:

• Sautéed mushrooms (drained well)
• 1 cup of cooked, sliced artichoke hearts
• A half-cup of sun-dried tomatoes (chopped)

These simple variations ensure that the delicious foundations of the Cheesy Collard Greens Gratin can be enjoyed by everyone, regardless of dietary preference, or adapted to suit your current craving.

Nutritional Breakdown and Health Benefits of Collard Greens

While this Cheesy Collard Greens Gratin is undeniably rich comfort food, it is built upon one of the most nutritionally dense leafy greens available. Collard greens (a member of the Brassica family, related to kale and cabbage) offer significant health benefits, allowing you to enjoy this decadent dish with fewer reservations.

Focus on Collard Greens

Collards are often touted as a “superfood” due to their impressive vitamin and mineral content, especially after cooking. Even braising them in stock retains much of their nutritional punch:

• Vitamin K Powerhouse: Collard greens are perhaps best known for their extremely high concentration of Vitamin K, essential for blood clotting and crucial for bone health. A single serving of collards often provides well over the daily recommended intake.
• Antioxidants and Detoxification: They are rich in antioxidants, including beta-carotene and Vitamin C. Furthermore, collards contain glucosinolates, which the body converts into compounds known to support detoxification pathways.
• High in Fiber: Collard greens provide ample dietary fiber, which aids digestion, promotes satiety, and helps regulate blood sugar levels. Even when braised until tender, they maintain their bulk.
• Immunity Support: The high level of Vitamin C in collards helps bolster the immune system.

Estimated Nutritional Values (Per Serving)

Given the inclusion of bacon, butter, flour, and a significant amount of dairy, this Cheesy Collard Greens Gratin is energy-dense. The following values are estimates for a generously sized serving (assuming 10 servings for the 9×13 dish):

While the cheese sauce contributes significantly to the calories and fat content, the large volume of nutrient-rich greens ensures that you are consuming a substantial amount of beneficial vitamins and minerals alongside the delicious comfort. Portion control is key with rich dishes like this, but knowing the dense nutritional core of the collard greens provides a guilt-free edge to enjoying this sumptuous side.

Frequently Asked Questions (FAQs) About Cheesy Collard Greens Gratin

We’ve gathered the most common questions related to preparing this beloved side dish, ensuring you achieve the perfect, creamy Cheesy Collard Greens Gratin every time.

Conclusion: A New Tradition with Cheesy Collard Greens Gratin

The journey from humble collard green to sophisticated casserole is complete. This Cheesy Collard Greens Gratin is a testament to how simple ingredients, combined with careful technique, can create a dish of extraordinary comfort and elegance. We’ve moved beyond basic braised greens, embracing the creamy indulgence of a three-cheese béchamel and the satisfying crunch of a Parmesan Panko topping.

This recipe balances the earthy robustness of collards with the smoky depth of bacon and the luxurious texture provided by Gruyère and cream cheese. Remember the foundational steps that guarantee success: meticulously remove the stems, braise until ultra-tender, and most importantly, drain the greens until they are nearly dry. Adhering to these steps will yield a sliceable, creamy, and non-watery gratin that will impress even the most discerning palate.

Whether you are looking for a show-stopping side for a holiday feast or simply wish to elevate your weeknight dinner, the Cheesy Collard Greens Gratin delivers warmth, flavor, and deep satisfaction. It holds its own beautifully next to rich roasts and poultry, offering a necessary green element that tastes anything but healthy! We encourage you to try this recipe, perhaps alongside another autumnal favorite like a creamy Butternut Squash Soup, for a truly comforting meal.

If you loved this recipe, please leave a comment below telling us how you served your gratin, and don’t forget to share this article with fellow food enthusiasts! Happy cooking!

Cheesy Collard Greens Gratin (A Southern Side Dish)

A luxurious twist on a Southern classic, fresh collard greens are slow-braised until tender, then smothered in a rich, velvety three-cheese sauce, topped with crispy Panko, and baked until bubbly.

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Prep Time 20 minutes mins

Cook Time 1 hour hr 25 minutes mins

Total Time 1 hour hr 45 minutes mins

Servings: 8 servings

Course: Casserole, Side Dish

Cuisine: American, Southern

Calories: 510

Ingredients Equipment Method Notes

Ingredients

  

For the Collard Greens

• 2.5 to 3 lbs fresh Collard Greens stems removed and coarsely chopped (approx. 2 large bunches)
• 4 cups Low-Sodium Chicken or Vegetable Stock
• 4 slices thick-cut Bacon diced (optional, but highly recommended)
• 1 medium Yellow Onion finely diced
• 3 cloves Garlic minced
• 1 teaspoon Red Pepper Flakes optional
• 2 tablespoons Apple Cider Vinegar
• Salt and freshly ground Black Pepper to taste

For the Rich Cheese Sauce (Bechamel Base)

• 4 tablespoons Unsalted Butter
• 1/4 cup All-Purpose Flour
• 3 cups Whole Milk or Half-and-Half warmed slightly
• 1/2 teaspoon Nutmeg freshly grated
• 8 ounces Sharp White Cheddar Cheese shredded
• 4 ounces Gruyère Cheese shredded
• 2 ounces Cream Cheese softened and cubed
• 1 teaspoon Kosher Salt
• 1/2 teaspoon Black Pepper

For the Topping

• 1 cup Panko Breadcrumbs
• 3 tablespoons Unsalted Butter melted
• 1/4 cup grated Parmesan Cheese

Equipment

• Large Dutch Oven or Stockpot
• 9x13 inch baking dish
• Large Colander
• Medium saucepan
• Whisk

Method

 

Part 1: Preparing and Cooking the Collard Greens

1. Prep the Oven and Baking Dish: Preheat your oven to 375°F (190°C). Lightly grease a 9x13 inch (or similarly sized 3-quart) baking dish.
2. Braise the Greens: In a large Dutch oven or stockpot, render the diced bacon over medium heat until crispy. Remove the bacon with a slotted spoon and set aside, leaving the fat in the pot.
3. Sauté Aromatics: Add the diced yellow onion to the bacon fat and sauté for 5 to 7 minutes until softened and translucent. Add the minced garlic and red pepper flakes (if using), and cook for 1 minute until fragrant.
4. Cook the Collards: Add the chopped collard greens to the pot. They will fill the pot completely, but will wilt quickly. Cook for 5 minutes, stirring often, until they begin to collapse.
5. Braise: Pour in the 4 cups of chicken or vegetable stock and the apple cider vinegar. Bring the mixture to a simmer, then cover the pot and reduce the heat to low. Let the greens braise for 45 minutes to 1 hour, or until they are very tender.
6. Drain Thoroughly: Drain the cooked collards completely using a large colander, pressing down firmly with the back of a spoon to remove as much liquid as possible. It is crucial the greens are dry so the final gratin is not watery. Set the drained greens aside in a large bowl.

Part 2: Making the Bechamel Cheese Sauce

1. Make the Roux: In a medium saucepan, melt the 4 tablespoons of butter over medium heat. Whisk in the flour and cook, stirring constantly, for 2 minutes to cook out the raw flour taste. This creates your roux.
2. Add Milk: Gradually whisk in the warm milk, adding about a cup at a time, ensuring all lumps are dissolved before adding the next batch. Continue whisking constantly until the sauce thickens significantly, usually about 8 to 10 minutes, until it coats the back of a spoon.
3. Season and Add Cheese: Remove the saucepan from the heat. Stir in the Kosher salt, black pepper, and nutmeg. Add the shredded sharp cheddar, Gruyère, and the cubed cream cheese. Stir gently until all the cheese has melted completely and the sauce is smooth, creamy, and velvety.

Part 3: Assembly and Baking

1. Combine: Pour the finished cheese sauce over the drained collard greens in the large bowl. Add the reserved crispy bacon bits (if using). Toss gently until the greens are thoroughly coated with the sauce.
2. Transfer to Dish: Pour the collard green and cheese mixture into the prepared 9x13 inch baking dish, spreading it into an even layer.
3. Prepare Topping: In a small bowl, combine the Panko breadcrumbs, melted butter, and grated Parmesan cheese. Toss until the breadcrumbs are evenly coated.
4. Final Bake: Sprinkle the Panko topping evenly over the collard greens mixture. Bake for 25 to 30 minutes, or until the sauce is bubbly around the edges and the breadcrumb topping is golden brown and crisp.
5. Rest and Serve: Allow the gratin to rest for 10 minutes before slicing and serving so the sauce can fully set.

Notes

For a vegetarian version, omit the bacon and use olive oil or butter to sauté the aromatics. Ensure your stock is vegetable stock. If you prefer a milder flavor, you can substitute the Gruyère with Monterey Jack or Provolone.