To prepare sauce, combine the first 5 ingredients; set aside.
Cut chicken across grain into 1/4-inch slices; cut slices into 1/2-inch-wide strips. Cut strips into 3-inch-long pieces.
Heat a 14-inch wok over high heat. Add 1 tablespoon oil to wok, swirling to coat. Add half of chicken to wok; stir-fry 2 minutes. Spoon cooked chicken into a bowl. Repeat procedure with 2 teaspoons oil and remaining chicken.
Add remaining 1 teaspoon oil to wok, swirling to coat. Add onion, ginger, and garlic to wok; stir-fry 1 minute or until lightly browned. Add curry powder and chiles; stir-fry 30 seconds. Add sauce and chicken to wok; stir-fry 1 minute. Spoon into a serving dish. Sprinkle with cilantro and cashews. Serve over rice.