In a medium bowl, combine the sliced steak, soy sauce, cornstarch, vegetable oil, sugar, and ground ginger. Mix well and let it marinate for at least 15 minutes (or up to 30 minutes in the refrigerator).
1 pound flank steak, 2 tablespoons soy sauce, 1 tablespoon cornstarch, 1 tablespoon vegetable oil, 1 teaspoon sugar, 1/2 teaspoon ground ginger
In a small bowl, whisk together the beef broth, soy sauce, oyster sauce (if using), cornstarch, sesame oil, and black pepper. Set aside.
1/2 cup beef broth, 2 tablespoons soy sauce, 1 tablespoon oyster sauce, 1 tablespoon cornstarch, 1 teaspoon sesame oil, 1/4 teaspoon black pepper
Heat 1 tablespoon of vegetable oil in a large skillet or wok over medium-high heat. Add the sliced onion and bell peppers. Stir-fry for 3-5 minutes, or until the vegetables are crisp-tender. Add the minced garlic and ginger and stir-fry for another 30 seconds, until fragrant. Remove the vegetables from the skillet and set aside.
1 tablespoon vegetable oil, 1 large onion, 2 bell peppers (any color), 2 cloves garlic, 1 teaspoon ginger
Add the remaining 1 tablespoon of vegetable oil to the skillet. Add the marinated steak and stir-fry for 3-5 minutes, or until browned and cooked through. Be careful not to overcrowd the pan; cook the steak in batches if necessary.
1 tablespoon vegetable oil, 1 pound flank steak
Return the stir-fried vegetables to the skillet. Pour the sauce over the steak and vegetables. Bring to a simmer and cook for 1-2 minutes, or until the sauce has thickened.
1 large onion, 2 bell peppers (any color), 1/2 cup beef broth, 2 tablespoons soy sauce, 1 tablespoon oyster sauce, 1 tablespoon cornstarch, 1 teaspoon sesame oil, 1/4 teaspoon black pepper
Serve immediately over rice or noodles. Garnish with sesame seeds or sliced green onions (optional).
