Preheat oven at 350. Prepare a 2 1/2-quart casserole dish with cooking spray; set aside. Cook noodles according to package directions. Drain. 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.