- In a bowl, combine the sliced flank steak, 2 tablespoons soy sauce, and cornstarch. Mix well and let marinate for 15 minutes. 
- In a large skillet or wok, heat 1 tablespoon of vegetable oil over medium-high heat. Add the marinated beef and stir-fry for about 3-4 minutes until browned. Remove the beef from the skillet and set aside. 
- In the same skillet, add the remaining tablespoon of vegetable oil. Add the broccoli, bell pepper, and carrots. Stir-fry for 3-5 minutes until the vegetables are tender-crisp. 
- Add the garlic, ginger, and green onions to the skillet and stir-fry for another minute until fragrant. 
- Return the beef to the skillet, then add the cooked chow mein noodles, oyster sauce, 2 tablespoons soy sauce, and sesame oil. Toss everything together and cook for an additional 2-3 minutes until heated through. 
- Serve hot and enjoy!