1. Coat the chicken with flour. Arrange in a single layer, skin side down, in melted butter in a 13 x 9 x 2-inch baking dish. Bake uncovered at 450 degrees F. for 30 minutes. Turn; bake until brown, about 15 to 20 minutes longer or until tender. Remove from oven. Reduce temperature to 325 degrees F.; pour off excess fat.
2. Combine milk, soup, cheese and salt and pepper. Add onions and mushrooms to chicken. Pour milk mixture over chicken. Sprinkle with paprika.
3. Cover dish with foil; return to oven and bake for 15 to 20 minutes.