Cook spaghetti according to package directions; rinse and drain. Cut chicken into bite-sized pieces. In a wok or skillet, heat the oil. Stir-fry chicken until done; remove and set aside. To wok, add onion, carrots, broccoli, and cauliflower; stir-fry for 1 minute. Add mushrooms and parsley; stir-fry 1 more minute. Return chicken to wok and cook for 2 more minutes. Add garlic salt, pepper, and soy sauce. Combine cornstarch and water. Add to chicken mixture and cook, stirring constantly, until mixture thickens. Toss with cooked spaghetti and serve immediately. Makes 6 servings.