Preheat your oven to 400°F (200°C).

Line a large, rimmed baking sheet with parchment paper or aluminum foil for easy cleanup. If using aluminum foil, lightly spray the surface with non-stick cooking spray to prevent the chicken from sticking.

Dry the Chicken Thighs: Remove the chicken thighs from their packaging and place them on a cutting board. Using paper towels, carefully pat the chicken thighs thoroughly dry. Removing excess moisture is crucial for achieving a nice, crisp exterior crust.

Mix the Seasoning Rub: In a small mixing bowl, combine all the ingredients for the ranch seasoning rub: the full packet of dry Ranch seasoning mix, garlic powder, onion powder, black pepper, and the optional Parmesan cheese. Stir until all ingredients are uniformly mixed.

Coat the Chicken: Place the dried chicken thighs into a large bowl. Drizzle the 2 tablespoons of olive oil (or melted butter) over the chicken and toss lightly to ensure the thighs are evenly coated in the fat. Sprinkle the prepared Ranch seasoning rub generously over all the chicken pieces. Use your hands or tongs to ensure every surface of the chicken thigh is thoroughly covered in the spice mixture.

Arrange the coated chicken thighs on the prepared baking sheet in a single layer, ensuring they are not touching each other. This allows the heat to circulate properly and encourages even cooking.

Bake: Place the baking sheet into the preheated 400°F oven. Bake for 25 to 30 minutes. The chicken is fully cooked when the internal temperature reaches 165°F (74°C) as measured by an instant-read meat thermometer inserted into the thickest part of the thigh.

Rest and Serve: Once cooked, carefully remove the baking sheet from the oven. Allow the chicken thighs to rest on the baking sheet for 5 to 10 minutes before serving. Garnish with fresh chopped parsley, if desired, and serve immediately.