I swear, the magic is in the sauce for this dish.

In a bowl, combine the sliced beef, soy sauce, and cornstarch. Let it marinate for about 15 minutes.

Heat 1 tablespoon of vegetable oil in a large skillet over medium-high heat. Add the marinated beef and stir-fry until browned. Remove the beef from the skillet and set aside.

In the same skillet, add the remaining tablespoon of vegetable oil. Add the sliced onion, green bell pepper, and red bell pepper. Stir-fry until the vegetables are tender-crisp.

Add the minced garlic to the skillet and stir-fry for another minute until fragrant.

Return the beef to the skillet. Add the oyster sauce, sugar, black pepper, and beef broth. Stir everything together and cook for another 2-3 minutes until the sauce thickens slightly.

Serve hot with your choice of sides.

For a spicier version, add a teaspoon of crushed red pepper flakes or a dash of hot sauce. You can also experiment with different vegetables such as mushrooms or snap peas for added texture and flavor. If you prefer a sweeter sauce, increase the amount of sugar slightly or add a splash of hoisin sauce. For a gluten-free option, use tamari instead of soy sauce and ensure the oyster sauce is gluten-free.