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 boil. Cook ravioli according to package directions, typically 3–5 minutes. Drain thoroughly in colander.
03 - In 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 mozzarella and Parmesan cheese evenly across surface.
05 - Cover dish tightly with aluminum foil. Bake for 20 minutes to heat through.
06 - Remove foil and continue baking 10–15 minutes until cheese turns golden brown and bubbly.
07 - Let casserole rest 5 minutes before garnishing with fresh parsley and serving warm.