01 - Set oven to 375°F. Lightly grease a 6-cup muffin tin.
02 - In a small bowl, mix together softened butter, minced garlic, and chopped parsley until well combined.
03 - Flatten each slice of bread with a rolling pin. Trim crusts as needed so slices fit snugly into muffin cups.
04 - Spread a thin layer of garlic butter on one side of each flattened bread slice, then press each slice butter-side-up inside a muffin cup, forming a nest shape.
05 - Sprinkle grated Parmesan cheese into the bottom of each prepared bread cup.
06 - Crack one large egg into each bread cup. Season with salt and black pepper. Add shredded mozzarella or cheddar cheese if desired.
07 - Place muffin tin in the oven. Bake for 16 to 18 minutes, or until egg whites are set and yolks reach preferred doneness.
08 - Allow cups to cool in the pan for 2 minutes. Use a small spatula to carefully lift each cup from the tin.
09 - Serve warm, garnished with extra parsley if desired.