Preheat oven to 350. Cook noodles according to package directions. Drain. Prepare the bottom of a 2.5-quart casserole dish with cooking spray; set aside. In a mixing bowl, combine noodles, chicken, onions, and broccoli. In another mixing bowl, combine soup, milk, cheese, basil, salt, and pepper. Stir in noodle mixture. Pour entire mixture into prepared dish. Bake, covered for 40 minutes.