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, usually 3-5 minutes. Drain well in a colander.
03 - In a large mixing bowl, combine the cooked ravioli, chicken, Alfredo sauce, milk, Italian seasoning, and black pepper. Mix gently to coat everything evenly without breaking the ravioli.
04 - Transfer the mixture to the prepared baking dish. Spread evenly. Sprinkle mozzarella and Parmesan cheese evenly over the top.
05 - Cover the baking dish tightly with aluminum foil. Bake for 20 minutes to heat through and meld flavors.
06 - Remove the foil and bake an additional 10-15 minutes, or until the cheese is golden brown and bubbly.
07 - Let the casserole rest for 5 minutes before serving to allow the sauce to thicken slightly. Garnish with chopped fresh parsley if desired.