Learnt this from my Beijing friend

1. Place the sliced flank steak in a bowl and toss with cornstarch until well-coated. Let it sit for a few minutes while you prep the vegetables.

2. Heat 1 tablespoon of vegetable oil in a large skillet or wok over medium-high heat. Once hot, add the beef in batches and stir-fry until crispy and browned, about 3-4 minutes per batch. Transfer the beef to a plate lined with paper towels to drain any excess oil.

3. Add the remaining tablespoon of oil to the skillet. Toss in the red and green bell peppers and the onion. Stir-fry for about 3-4 minutes, until the vegetables begin to soften.

4. Add the minced garlic and ginger to the skillet, and cook for about 30 seconds until fragrant.

5. In a small bowl, whisk together the soy sauce, oyster sauce, hoisin sauce, rice vinegar, sugar, and red pepper flakes (if using).

6. Return the beef to the skillet, pour the sauce over the top, and toss everything together to coat evenly. Cook for an additional 2-3 minutes until everything is heated through and the sauce has slightly thickened.

7. Garnish with sesame seeds and sliced green onions before serving.

If you’re looking to mix things up, try using chicken or shrimp instead of beef. For a healthier version, you can skip the cornstarch and fry the beef simply without the coating. Vegetables such as broccoli or snap peas can be added or substituted based on your preference. Feel free to adjust the sweetness and tanginess of the sauce by playing with the amount of sugar and vinegar. For those with dietary restrictions, tamari can replace soy sauce for a gluten-free option.