Prepare barley according to package directions. In a small bowl, combine water, soy sauce and cornstarch; set aside. In a large skillet or wok, saute garlic in oil for 15 seconds. Add carrots; stir-fry for 1 minute. add broccoli and onions; stir-fry for 2-3 minutes. Stir in soy sauce mixture; simmer and stir for 1 minute or until thickened. Add chicken an barley; heat through. Stir in peanuts if desired.