01 - Preheat oven to 375°F (190°C) and lightly grease a 6-cup muffin tin.
02 - In a small bowl, blend the softened butter with minced garlic and chopped parsley until thoroughly combined.
03 - Flatten each bread slice using a rolling pin. Trim crusts as needed so each piece fits snugly into the muffin cups.
04 - Spread a thin layer of garlic butter onto one side of each bread slice. Press each slice, butter-side-up, into a muffin cup to form individual nests.
05 - Sprinkle a portion of grated Parmesan cheese at the base of each assembled bread cup.
06 - Crack one egg into each prepared bread cup. Season with salt and black pepper and add shredded mozzarella or cheddar cheese if desired.
07 - Bake for 16 to 18 minutes, or until egg whites are fully set and yolks reach preferred doneness.
08 - Allow bread cups to cool in the tin for 2 minutes, then carefully remove each using a small spatula. Serve warm, garnished with extra chopped parsley if desired.