Combine first 6 ingredients in a bowl. Reserve. In a separate bowl combine beef with ¼ cup (50 mL) reserved sauce.
Combine cornstarch and water. Reserve.
Heat large non-stick skillet over medium-high heat. Add oil. When pan is hot, add beef. Cook until outside of beef is cooked, about 2 minutes. Add frozen vegetables and sauce. Bring sauce to a boil, cook, stirring constantly for 2-3 minutes until vegetables and beef are cooked through. Add cornstarch mixture. Cook, stirring constantly until thickened, about 1 minute.
Variations: Replace beef with shrimp or thinly sliced chicken. Serve with rice or noodles.