01 - Preheat oven to 375°F. Lightly grease a 2-quart baking dish.
02 - In a large bowl, whisk together eggs, whole milk, heavy cream, salt, black pepper, and nutmeg until well blended.
03 - Add shredded sharp cheddar and mozzarella cheeses to the wet mixture; stir to combine evenly.
04 - Fold in 1 cup of the fresh breadcrumbs gently to maintain texture.
05 - Pour the cheese mixture into the prepared baking dish and spread it evenly.
06 - In a small bowl, mix remaining 1 cup breadcrumbs with melted butter and grated Parmesan if using; sprinkle this topping evenly over the casserole.
07 - Bake for 30 to 35 minutes until the casserole is firm and the top is golden brown.
08 - Allow to cool for 5 minutes, then garnish with chopped parsley before serving.