Let’s bring this flavorful dish to life with these simple steps:

1. In a medium bowl, combine the sliced flank steak with soy sauce, oyster sauce, sesame oil, and cornstarch. Mix well and let it marinate for at least 10 minutes.
2. Heat vegetable oil in a large wok or skillet over medium-high heat. Once hot, add the marinated beef in a single layer. Cook for 3-4 minutes, or until browned and cooked through. Remove beef from the pan and set aside.
3. In the same pan, add the garlic and ginger. Sauté for 30 seconds until fragrant.
4. Add the bell pepper, broccoli, and snow peas to the pan. Stir-fry for 5-7 minutes, until the vegetables are crisp-tender.
5. Return the beef to the pan, toss everything together, and heat through for another 2 minutes. Season with salt and pepper to taste.
6. Sprinkle with sesame seeds before serving, if desired.

Remember, cooking is all about intuition—if the veggies start to look too soft, lower the heat and give them a stir. It’s something my abuela taught me, and it never fails!