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 well in a colander.
03 - In a large mixing bowl, combine cooked ravioli, chicken, Alfredo sauce, milk, Italian seasoning, and black pepper. Gently fold together until evenly coated.
04 - Transfer mixture to prepared baking dish. Spread evenly. Sprinkle mozzarella and Parmesan cheese across the top 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 10-15 minutes until cheese is golden brown and bubbly around edges.
07 - Let casserole rest 5 minutes before serving. Sprinkle with fresh chopped parsley if desired.