Place chicken in a 4- or 5-qt. slow cooker. Top with mushrooms, celery, onion, bean sprouts, bamboo shoots and water chestnuts. In a small bowl, combine the broth, soy sauce, ginger and pepper flakes. Pour over chicken and vegetables. Cover and cook on low until chicken is tender, 5-6 hours., Combine cornstarch and water until smooth; gradually stir into chop suey. Add edamame, cover and cook on high until thickened, about 30 minutes. Serve with rice.