Add chicken to reserved drippings in skillet; cook 2 min. on each side or until each breast is lightly browned on both sides. Remove chicken from skillet; set aside. Add vegetables to skillet; cook 3 to 5 min. or until onions are softened, stirring frequently. Add flour; cook and stir 1 min. Stir in broth and water; bring to boil, stirring frequently.