01 - Preheat oven to 375°F. Lightly grease a 6-cup muffin tin.
02 - In a small bowl, mix softened butter with minced garlic and chopped parsley until well combined.
03 - Flatten each bread slice evenly using a rolling pin. Trim crusts if needed for a precise fit within muffin cups.
04 - Spread a thin layer of garlic butter on one side of each flattened bread slice. Press each slice, butter-side-up, into the muffin tin to create a well-formed nest.
05 - Distribute grated Parmesan cheese evenly into the bottom of each bread-lined cup.
06 - Crack one egg into each bread cup. Season with salt and black pepper. If desired, sprinkle shredded mozzarella or cheddar cheese over each egg.
07 - Bake in the preheated oven for 16 to 18 minutes, until egg whites are set and yolks reach preferred doneness.
08 - Let cool in the tin for 2 minutes. Gently loosen and lift each egg cup using a small spatula. Serve warm, garnished with extra parsley if desired.