01 - Preheat oven to 375°F. Lightly grease a 6-cup muffin tin.
02 - In a small bowl, blend softened butter with minced garlic and chopped parsley until evenly combined.
03 - Flatten each bread slice using a rolling pin. Trim crusts as needed to fit the muffin cups.
04 - Spread a thin layer of garlic butter on one side of each piece of bread. Press each slice, buttered side up, into the muffin tin wells to shape a cup.
05 - Sprinkle grated Parmesan cheese evenly into the bottom of each bread cup.
06 - Carefully crack one egg into each bread cup. Season with salt and black pepper. Scatter shredded mozzarella or cheddar cheese over each, if desired.
07 - Place in oven and bake for 16 to 18 minutes, or until egg whites are set and yolks reach desired doneness.
08 - Allow to rest for 2 minutes, then gently release each cup from the tin using a small spatula.
09 - Serve warm. Garnish with extra fresh parsley if desired.