01 - Preheat oven to 375°F. Lightly grease a 9x13-inch baking dish with cooking spray or butter.
02 - Bring a large pot of salted water to a boil. Cook ravioli according to package directions, typically 3–5 minutes. Drain thoroughly in a colander.
03 - In a large mixing bowl, add cooked ravioli, shredded chicken, Alfredo sauce, milk, Italian seasoning, and black pepper. Gently fold together until evenly coated.
04 - Transfer mixture to the prepared baking dish. Spread evenly and top with mozzarella and Parmesan cheeses in a uniform layer.
05 - Cover dish tightly with aluminum foil. Bake for 20 minutes to heat through and meld flavors.
06 - Remove foil and continue baking for 10–15 minutes until cheese is melted and golden brown with bubbling edges.
07 - Let casserole rest for 5 minutes before serving. Garnish with fresh chopped parsley if desired.