1. In a bowl, mix soy sauce, garlic, ginger, and chili flakes. Marinate thinly sliced beef in the mixture for 30 minutes.

2. Heat oil in a wok or skillet. Stir-fry marinated beef until cooked through. Remove from pan.

3. Add sliced bell peppers, onions, and broccoli to the same pan. Stir-fry until vegetables are tender-crisp.

4. Return beef to the pan. Add a mixture of soy sauce, oyster sauce, and sugar. Stir well to combine.

5. Serve hot over steamed rice or noodles.