Stir- Fried Beef Teriyaki

In a bowl mix 2 teaspoons cornstarch, 3 tablespoons teriyaki sauce, 2 teaspoons vegetable oil and add ½ kilo beef round which have been cut into strips. Refrigerate for about 45 minutes. Meantime stir-fry 6 spring onions which have been thinly sliced and 2 bell peppers (thinly sliced) in 2 teaspoons vegetable oil for 3 minutes. Remove from pan and then stir-fry the marinated beef for another three minutes. Stir in the vegetables and cook until beef is done.