Combine soy sauce and 1 tablespoon cornstarch; mix well. add chicken, and stir until coated; set aside.
heat 1 tablespoon oil in wok until hot; add nuts, stirring constantly, until browned (about 3o seconds). remove nuts, and set aside. add another tablespoon oil to pan; add chicken, and stir-fry 1 to 2 minutes. remove chicken, and set aside.
cut onion into 1/4-inch slices; cut slices in half crosswise. add remaining oil to wok, and heat to smoking. add vegetables and garlic; cover and cook 1 minute, shaking wok to prevent vegetables from sticking. remove cover; cook, stirring constantly, an additional 2 to 4 minutes.
combine broth and 1 teaspoon cornstarch. add chicken and broth mixture to vegetables; stir until thickened. stir in cashews. yield: 2 servings.