Creating your own Beijing Beef is straightforward if you follow these simple steps:

1. Prepare the Beef: Start by slicing the flank steak into thin strips against the grain. This will ensure the meat remains tender when cooked.

2. Marinate the Beef: In a bowl, combine the soy sauce, brown sugar, and cornstarch. Add the sliced beef, ensuring it’s well coated. Let it marinate for about 10 minutes.

3. Heat the Oil: In a large pan or wok, heat the vegetable oil over medium-high heat.

4. Cook the Beef: Add the marinated beef to the hot pan in a single layer. Cook for 3-4 minutes, allowing it to sear and brown. Stir occasionally to ensure even cooking.

5. Add Aromatics: Once the beef is nearly cooked, add the minced garlic and ginger to the pan. Stir-fry for about 30 seconds until fragrant.

6. Add Vegetables: Toss in the sliced bell peppers and onions. Stir-fry for an additional 3-4 minutes until the vegetables are tender but still crisp.

7. Make the Sauce: In a small bowl, mix the remaining soy sauce and red pepper flakes. Pour this mixture over the beef and vegetables in the pan. Stir to combine and let it simmer for 1-2 minutes to thicken.

8. Serve: Remove from heat and serve the Beijing Beef over a bed of cooked rice or noodles.

9. Garnish: If desired, sprinkle sesame seeds and sliced green onions on top for added flavor and a pop of color.

These steps will help you create a mouthwatering Beijing Beef dish that everyone will love!