Cut the beef across the grain into thin strips, remove any excess fat, and throw it away. Place beef strips in a bowl with 5 mL (1 tsp.) cornstarch and the soy sauce. Marinate for 10 minutes.

Heat 10 mL (2 tsp.) oil in a large skillet over medium-high heat. Sauté the beef until no longer pink, about 3 minutes. Place the beef in a dish.

Return skillet to stove and heat remaining oil. Add broccoli and red pepper and sauté until tender-crisp, about 3 minutes. 

Add beef and teriyaki cooking sauce, stirring to coat the beef, and cook until the mixture is very hot. 

Whisk together the remaining cornstarch and beef broth in a small bowl until smooth. Pour into skillet. 

Bring to a boil, stirring constantly. Reduce heat and simmer until sauce thickens, about 2 minutes.

Transfer to a serving dish and garnish with green onions.