In a bowl, combine cornstarch, sugar & salt. Add chicken & toss. Heat wok or frying pan to highest heat. Add oil. Heat to hot, not smoking. Add chicken, ginger, garlic & onion. Stir until chicken is opaque (about 1 minute). Add peppers and carrots. Stir 2-3 minutes. Add peas and sauce. Cook until it comes to a boil. Add cashews and serve immediately.