01 - In a shallow bowl, thoroughly whisk together eggs, whole milk, finely minced garlic, Italian herbs, salt, and black pepper until evenly combined.
02 - Arrange all bread slices on a clean surface. Evenly distribute half the mozzarella and cheddar cheeses over 4 slices, then cover with the remaining bread to create sandwiches.
03 - Gently dip each sandwich into the prepared egg mixture, allowing both sides to absorb liquid for approximately 10 seconds per side.
04 - Warm unsalted butter and olive oil together in a large nonstick skillet set over medium heat.
05 - Carefully transfer the soaked sandwiches into the hot skillet. Cook for 4 to 5 minutes per side, applying gentle pressure with a spatula, until bread is golden brown and cheese is melted.
06 - Remove from skillet and immediately sprinkle each stack with freshly grated Parmesan cheese and chopped parsley. Cut each stack in half if desired, and serve while hot.