01 - Preheat oven to 375°F. Lightly grease a six-cup muffin tin.
02 - In a small bowl, blend the softened butter with minced garlic and chopped parsley until evenly combined.
03 - Flatten each bread slice with a rolling pin and trim crusts as needed to fit the muffin tin.
04 - Spread a thin layer of garlic butter onto one side of each bread slice. Press each slice, buttered side up, into the muffin tin cavities to form nests.
05 - Sprinkle a small amount of grated Parmesan cheese into the base of each bread cup.
06 - Crack one egg into each bread-lined cup. Season with salt and black pepper. Top with shredded mozzarella or cheddar cheese if desired.
07 - Bake for 16 to 18 minutes, or until the egg whites are just set and yolks have reached preferred doneness.
08 - Allow cups to cool for 2 minutes. Use a small spatula to carefully lift each egg cup from the tin.
09 - Serve warm. Garnish with additional chopped parsley if desired.