01 - Preheat oven to 375°F (190°C) and lightly grease a 6-cup muffin tin.
02 - In a small bowl, blend softened butter with minced garlic and chopped parsley until well combined.
03 - Flatten each bread slice using a rolling pin. Trim crusts if necessary so bread fits snugly into each muffin cup.
04 - Spread a thin layer of garlic butter on one side of each bread slice. Place each slice butter-side up into the muffin tin, pressing gently to form a cup.
05 - Sprinkle grated Parmesan cheese into the base of each bread cup.
06 - Crack one egg into each bread cup. Season eggs with salt and black pepper. Add shredded mozzarella or cheddar cheese on top if desired.
07 - Bake for 16 to 18 minutes, or until egg whites are set and yolks reach preferred doneness.
08 - Let egg cups cool for 2 minutes, then carefully remove from the tin with a small spatula.
09 - Serve warm, garnished with extra chopped parsley if desired.