Preheat oven to 350. Coat a 3 quart rectangular baking dish with nonstick cooking spray. Set aside
Cook noodles as pkg. directs. Drain well. Rinse with cold water, drain well again.
Meanwhile, coat an unheated large skillet with nonstick cooking spray. Preheat over medium heat. Add chicken to hot skillet. Cook and stir about 3 minutes or til chicken is no longer pink. Transfer chicken to large bowl.
Add mushrooms, the 8 green onions, and sweet red pepper to skillet. Cook and stir til vegetables are tender. If needed, add 1 Tbsp. vegetable oil to skillet.
Transfer vegetables to bowl with chicken. Stir in cream of broccoli soup, sour cream broth, mustard and black pepper. Gently stir in cooked noodles and broccoli.
Spoon chicken mixture into prepared dish. Mix bread crumbs and melted butter; Sprinkle over chicken mixture. Cover dish with foil. Bake for 30 minutes. Uncover and bake about 30 minutes or til heated through. If desired, garnish with bias sliced green onions. Makes 12 servings.