Instructions:
Marinate the Beef: In a medium bowl, combine the sliced flank steak, 2 tablespoons soy sauce, and cornstarch. Mix well and let it marinate for 15 minutes.
Cook the Beef: In a large skillet or wok, heat the vegetable oil over medium-high heat. Add the marinated beef and stir-fry until browned and cooked through, about 4-5 minutes. Remove the beef from the skillet and set aside.
Stir-fry the Vegetables: In the same skillet, add the sliced onion and bell peppers. Stir-fry for 3-4 minutes until the vegetables are tender-crisp.
Add Aromatics: Add the minced garlic and ginger to the skillet and stir-fry for another 1-2 minutes until fragrant.
Prepare the Sauce: In a small bowl, whisk together the 1/4 cup soy sauce, beef broth, oyster sauce, hoisin sauce, sugar, black pepper, and red pepper flakes (if using).
Combine and Cook: Return the cooked beef to the skillet and pour the sauce mixture over the beef and vegetables. Stir to combine and cook for another 2-3 minutes until the sauce has thickened and everything is heated through.
Serve: Serve the pepper steak over cooked rice and garnish with chopped green onions
