Coat a 13x9x2-inch baking dish with cooking spray. Set aside.
Cook noodles according to package directions, except omit salt or oil. Drain. Rinse with cold water and drain.
Coat a large skillet with more cooking spray. Add the chicken. Cook and stir over medium heat for 3 minutes or until chicken is no longer pink. Transfer the mixture from the skillet to a large mixing bowl.
Add mushrooms, green onions, red pepper, broth, and garlic to skillet. Bring to boiling. Reduce heat. Simmer, covered, about 3 minutes or until vegetables are tender.
Transfer to large bowl with chicken. Add soup, sour cream, mustard, and pepper to chicken mixture. Gently stir in the noodles and broccoli.
Spoon into prepared baking dish. Mix bread crumbs and melted butter. Sprinkle over noodles. Cover with foil. Bake in a 350 degree F oven for 30 minutes. Remove foil. Bake 10 to 15 minutes more or until heated through. Makes 8 servings.