In a small bowl, combine the steak strips with 1 tablespoon soy sauce, garlic powder, and 1 tablespoon of cornstarch. Mix well until combined. Let it marinate in the fridge for at least 30 minutes.
In another bowl, make the sauce for the stir-fry. Combine the remaining soy sauce, cornstarch, chopped ginger, and brown sugar. Stir well. In a large skillet, heat the sesame oil on HIGH then add the marinated steak strips.