Cook noodles according to directions and set aside. Preheat oven to 350. Coat a 9x13 baking dish with cooking spray; set aside.
In a medium saucepan over low heat, melt butter' gradually add flour, stirring until smooth. Cook 1 minute, stirring constantly. Gradually add chicken broth and milk; increase heat to medium and cook until mixture is slightly thickened and bubbly, stirring constantly. Stir in salt and pepper; set aside.
In a large bowl combine noodles, chicken, mushrooms, onion and parsley; stir in sauce. Spoon mixture into baking dish and sprinkle with cheese.
Bake uncovered 25 minutes or until heated through.