Ginger Beef and Mushroom Stir-Fry

Mix soy sauce, vinegar, sugar, sesame oil, and cornstarch together in small measuring cup until smooth. Pour half into a medium bowl for marinade and set the remainder aside. Slice steak across the grain into very thin slices. Add to marinade and let stand for 20 minutes. Meanwhile cook rice according to package directions and separate bok choy leaves from stalks; set aside.

Heat 2 tsp (10 mL) of the oil in large non-stick skillet or wok over medium-high heat until hot; add ginger root, garlic and pepper flakes (if using) and stir-fry for 30 seconds or until fragrant but not browned. Remove beef from marinade with slotted spoon; add to hot skillet and stir-fry for 2 to 3 minutes or until browned. Transfer to bowl; keep warm.

Add remaining oil to the skillet and cook bok choy stalks, carrots, onions and mushrooms, stir-frying for 3 to 5 minutes. Add broth and corn (if using); cover and cook for 2 to 3 minutes or until vegetables are just tender-crisp. Stir in bok choy leaves and push vegetables to the side of skillet. Pour reserved soy sauce mixture and leftover marinade into middle of skillet; bring to boil for 1 minute, stirring constantly until slightly thickened. Return beef mixture along with any accumulated juices to skillet and add peanuts; toss with vegetables and heat through.

Serve over hot rice and garnish with cilantro or green onions.