Preheat your oven to 350°F (175°C). Thoroughly grease a standard 12-cup muffin tin with non-stick cooking spray or butter. Ensure all surfaces of the cups are completely coated.

If not already done, cook the 6 slices of bacon until very crispy. Blot away excess grease and crumble them into small, bite-sized pieces. Set aside.

In a large mixing bowl, crack all 12 large eggs. Add the heavy cream (or milk), salt, and black pepper.

Whisk the mixture vigorously for 1 to 2 minutes until the eggs are fully incorporated, slightly frothy, and a uniform light yellow color. The added air helps create a fluffy texture.

Gently fold the shredded cheddar cheese and the crumbled bacon pieces into the egg mixture. If using, stir in the optional chopped chives or green onion.

Carefully pour the egg mixture into each prepared muffin cup, filling them evenly about three-quarters of the way full. Do not overfill, as they will puff slightly.

Bake for 20 to 25 minutes. The egg bites are done when they are set, puffy, lightly golden around the edges, and a toothpick inserted into the center comes out clean.

Remove the muffin tin from the oven and allow the egg bites to cool in the pan for 3 to 5 minutes. This step helps them firm up and prevents them from sticking or deflating rapidly.

Using a small offset spatula or butter knife, gently run the blade around the edge of each egg bite to loosen it, then carefully lift them out and transfer them to a serving plate. Serve warm.