01 - Whisk eggs, milk, salt, and black pepper in a mixing bowl until thoroughly blended.
02 - Place a 10-inch non-stick skillet over medium heat and coat evenly with unsalted butter.
03 - Add minced garlic and sauté for 30 seconds until aromatic but not browned.
04 - Pour the egg mixture into the skillet and cook gently, stirring with a spatula, until eggs start to set but remain slightly soft on top, about 2 minutes.
05 - Evenly sprinkle cheddar and mozzarella cheeses over the eggs; scatter parsley if desired.
06 - Lay the flour tortilla directly onto the egg-cheese mixture, pressing lightly with a spatula. Continue cooking 1 to 2 minutes until eggs are almost fully set.
07 - Use a large spatula, or invert the pan onto a plate then slide back into the skillet, to flip so the tortilla is now on the bottom.
08 - Cook for 1 to 2 minutes until the tortilla is crispy and golden.
09 - Transfer to a plate, fold in half, slice, and serve immediately while hot.