- Cut chicken into narrow strips. Mix 1 Tbsp. each cornstarch and teriyaki sauce with ginger; stir in chicken. Let stand 10 minutes.
- Meanwhile, combine remaining 1 Tbsp. cornstarch, 3 Tbsp. teriyaki sauce and 3/4 cup water.
- Cut bok choy crosswise into 2-inch wide pieces.
- Heat 1 Tbsp. oil in wok or large skillet over high heat. Add chicken and stir-fry 1 minute; remove.
- Heat 2 Tbsp. remaining oil in same wok. Add bok choy stems, onion and mushrooms; stir-fry 4 minutes. Add leaves; stir-fry 1 minute. Add chicken and teriyaki sauce mixture; cook and stir until sauce boils and thickens. *Or, use romaine lettuce instead.