1️⃣ Marinate the Beef:

1. In a bowl, combine the sliced beef with soy sauce, cornstarch, and vegetable oil. Mix well to coat the beef evenly and let it marinate for at least 15 minutes.

2️⃣ Prepare the Sauce:

1. In a small bowl, mix the soy sauce, oyster sauce, sugar, black pepper, and water. Set aside.

3️⃣ Stir-Fry the Beef:

1. Heat 1 tablespoon of vegetable oil in a wok or large skillet over medium-high heat. Add the marinated beef in a single layer and sear for 1-2 minutes per side until browned. Remove the beef from the pan and set aside.

4️⃣ Sauté the Aromatics:

1. Add the remaining tablespoon of vegetable oil to the pan. Stir-fry the onion wedges and garlic for 2-3 minutes until the onions are slightly softened but still crisp. Add the green onions and ginger (if using) and stir-fry for another minute.

5️⃣ Combine and Finish:

1. Return the beef to the pan and pour in the sauce. Stir well to coat the beef and vegetables in the sauce. Let it cook for 2-3 minutes until the sauce thickens slightly.

6️⃣ Garnish and Serve:

1. Sprinkle with sesame seeds and serve immediately over steamed rice or noodles.