Prepare noodles according to package directions. Saute peppers, onions and mushrooms in butter. Add cornstarch, salt and pepper; add chicken broth all at once; add dry milk; cook until thick and bubbly. Combine meat and cheese; add to sauce. Turn into 1 1/2 quart casserole; bake until cheese metls (about 15 minutes). Serve over noodles. Bake in oven at 350 degrees.