1. Whisk together soy sauce, sesame oil, cornstarch, chile-garlic sauce (if using), and 1/2 cup water in small bowl. Set aside.
2. Heat vegetable oil in wok over high heat. Add onion, bell pepper, cashews, and ginger, and stir-fry 2 to 3 minutes, or until onion and cashews begin to brown. Add snap peas, and stir-fry 1 minute. Add snow peas and green onions, and stir-fry 2 to 3 minutes more. Add soy sauce mixture, and cook 1 to 2 minutes more, or until sauce has thickened and vegetables are coated with sauce.