01 - Preheat oven to 375°F and 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 for 3-5 minutes until al dente. 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 all components are evenly coated.
04 - Transfer mixture to the prepared baking dish and spread into an even layer. Sprinkle mozzarella and Parmesan cheese uniformly across the surface.
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, golden brown, and bubbly around the edges.
07 - Let casserole rest for 5 minutes before serving. Garnish with fresh chopped parsley if desired.