Follow these steps carefully for a foolproof, restaurant-quality stir-fry. The key is to have all your ingredients prepped and ready to go before you turn on the heat, a practice known as mise en place.

Step 1: Prepare and Marinate the Beef (Velveting)

1. Place your steak in the freezer for 15-20 minutes. This firms up the meat, making it much easier to slice thinly.
2. Remove the steak and, using a sharp knife, slice it very thinly (about 1/8-inch thick) against the grain. Slicing against the grain is crucial for tenderness, as it shortens the muscle fibers.
3. In a medium bowl, combine the sliced beef with 1 tablespoon of soy sauce, 1 tablespoon of cornstarch, and 1 teaspoon of sesame oil. Use your hands or tongs to toss everything together until each slice of beef is evenly coated. Set aside to marinate for at least 15 minutes at room temperature while you prepare the other ingredients.

Step 2: Prepare the Green Beans and Sauce

1. Bring a small pot of salted water to a boil. Add the trimmed green beans and blanch them for 2-3 minutes. They should turn bright green and become slightly tender but still have a crisp bite.
2. Immediately drain the green beans and rinse them under cold water or plunge them into an ice bath. This stops the cooking process and preserves their vibrant color and crunch. Pat them dry and set aside.
3. In a small bowl, whisk together all the ingredients for the stir-fry sauce: 1/4 cup soy sauce, oyster sauce, brown sugar, Shaoxing wine (if using), 1 teaspoon sesame oil, white pepper, 1 tablespoon cornstarch, and 1/4 cup of water or beef broth. Whisk until the cornstarch is fully dissolved and the mixture is smooth. Set this aside near your stove.

Step 3: Cook the Stir-Fry

1. Heat a large skillet or wok over high heat until it is smoking slightly. A very hot pan is essential for getting a good sear.
2. Add 1 tablespoon of the high-smoke-point oil to the hot wok. Carefully add the marinated beef in a single, even layer. Do not overcrowd the pan; cook in two batches if necessary.
3. Let the beef sear, undisturbed, for 1-2 minutes until a deep brown crust forms on the bottom. Then, use a spatula to flip and stir-fry for another 1-2 minutes until it’s just cooked through. The beef will cook very quickly.
4. Remove the cooked beef from the wok and place it on a clean plate.

Step 4: Assemble the Dish

1. Return the wok to high heat. Add the remaining 1 tablespoon of oil.
2. Add the minced garlic and grated ginger to the wok and stir-fry for about 30 seconds until fragrant. Be careful not to burn them.
3. Add the blanched and dried green beans to the wok. Stir-fry for 2-3 minutes, tossing them with the garlic and ginger until they are heated through.
4. Give your prepared sauce a quick re-whisk (the cornstarch may have settled) and pour it into the wok over the green beans.
5. Bring the sauce to a simmer. It will begin to thicken and turn glossy almost immediately, thanks to the cornstarch.
6. Return the cooked beef and any accumulated juices back to the wok. Toss everything together for about 1 minute to coat the beef and beans in the thickened sauce.
7. Remove from the heat immediately. Serve hot, garnished with toasted sesame seeds and sliced green onions if desired.