In a bowl whisk together 2 tablespoons cornstarch with ginger powder, beef broth and soy sauce and black pepper; set aside.
In another medium bowl combine 2 tablespoons cornstarch with 1/2 teaspoon salt, add in the steak strips; toss to coat with the mixture.
Heat vegetable oil and 2 teaspoons sesame oil in a large skillet over high heat; add in the beef/cornstarch mixture and saute for about 4 minutes or until browned, adding in the garlic and chili flakes (if using) the last 2 minutes of cooking.
Add in the bell pepper and onion; saute for about 6-8 minutes or until tender.
Add in the broth mixture; reduce heat and simmer for about 3-5 minutes or until thickened.