01 - Set the oven to 375°F. Lightly grease a 2-quart baking dish to prevent sticking.
02 - In a large mixing bowl, whisk together the eggs, whole milk, heavy cream, salt, black pepper, and ground nutmeg until fully blended.
03 - Stir in the shredded sharp cheddar and mozzarella cheeses until evenly distributed.
04 - Fold in 1 cup of the fresh breadcrumbs gently to maintain a uniform mixture.
05 - Pour the prepared cheese and breadcrumb mixture into the greased baking dish and spread evenly.
06 - Combine the remaining 1 cup breadcrumbs with melted unsalted butter, and if desired, grated Parmesan cheese. Sprinkle this topping evenly over the surface.
07 - Bake the casserole for 30 to 35 minutes, or until the custard is fully set and the topping turns golden brown.
08 - Allow to cool for 5 minutes, then garnish with chopped fresh parsley before serving.