01 - Preheat your 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 the ravioli according to package directions, typically 3–5 minutes. Drain well in a colander.
03 - In a large mixing bowl, combine the cooked ravioli, shredded chicken, Alfredo sauce, milk, Italian seasoning, and black pepper. Gently fold together until evenly coated.
04 - Transfer the mixture to the prepared baking dish, spreading evenly. Sprinkle the mozzarella and Parmesan cheese over the top in a uniform layer.
05 - Cover the dish tightly with aluminum foil. Bake for 20 minutes to heat through and meld flavors.
06 - Remove the foil and continue baking for an additional 10–15 minutes, until the cheese is melted and golden brown with bubbly edges.
07 - Let the casserole rest for 5 minutes before serving. Garnish with fresh chopped parsley if desired.