Follow these steps closely, paying attention to the techniques. The key to a great stir-fry is preparation and speed. Have all your ingredients prepped and ready to go before you even think about turning on the stove. This concept is known as mise en place (“everything in its place”), and it’s non-negotiable for stir-frying.

Step 1: Prepare the Beef

1. Slice the Beef: Place your steak in the freezer for 15-20 minutes. This firms it up, making it significantly easier to slice thinly. Remove the partially frozen steak and, using a sharp knife, slice it as thinly as possible (about 1/8-inch thick) against the grain. This is crucial for tenderness. To find the grain, look for the parallel lines of muscle fiber in the meat, and slice perpendicular to them.
2. Marinate the Beef: In a medium bowl, combine the sliced beef with 1 tablespoon of the soy sauce and 1 teaspoon of the cornstarch. Use your hands or tongs to toss the beef thoroughly, ensuring every piece is coated. This simple marinade not only adds flavor but the cornstarch creates a protective barrier that locks in moisture, a technique known as velveting. Set the beef aside to marinate for at least 15 minutes while you prepare the other ingredients.

Step 2: Prepare the Vegetables and Sauce

1. Blanch the Green Beans (Optional but Recommended): Bring a pot of salted water to a rolling boil. Add the trimmed green beans and cook for 2-3 minutes, just until they turn a vibrant, bright green and are slightly tender but still have a firm bite. Immediately drain the beans and plunge them into a bowl of ice water (an “ice bath”). This stops the cooking process instantly, locking in that beautiful color and crisp texture. Drain well and set aside.
2. Mix the Stir-Fry Sauce: In a small bowl or liquid measuring cup, whisk together the remaining 3 tablespoons of soy sauce, honey, rice vinegar, the remaining 2 teaspoons of cornstarch, black pepper, and the water or beef broth. Whisk until the cornstarch is fully dissolved and the sauce is smooth. Set this bowl right next to your stove.
3. Prepare Aromatics: Ensure your garlic is minced, ginger is grated, and onion is sliced. Have them in small bowls next to the stove alongside your blanched green beans and marinated beef.

Step 3: The Stir-Fry

1. Heat the Pan: Place a large wok or a heavy-bottomed skillet (cast iron is excellent) over high heat. Let the pan get screaming hot. You should see faint wisps of smoke rising. This high heat is essential for getting a proper sear and avoiding steaming the ingredients.
2. Sear the Beef: Add the tablespoon of avocado oil to the hot pan. It should shimmer immediately. Carefully add the marinated beef in a single layer. Do not overcrowd the pan; work in two batches if necessary. Let the beef sear undisturbed for 1-2 minutes until a deep brown crust forms on the bottom. Then, stir-fry for another 1-2 minutes until it’s just cooked through. The beef will cook very quickly. Remove the cooked beef from the pan with a slotted spoon and set it aside on a plate.
3. Sauté the Aromatics: Reduce the heat slightly to medium-high. If the pan is dry, add a tiny bit more oil. Add the sliced onions and cook for 1-2 minutes until they begin to soften. Add the minced garlic and grated ginger and stir-fry continuously for about 30 seconds until they are fragrant. Be very careful not to burn them, as burnt garlic will make the dish bitter.
4. Combine and Sauce: Add the blanched green beans to the pan and toss with the aromatics for 1 minute to heat them through. Return the cooked beef to the pan. Give your prepared sauce a quick re-whisk (the cornstarch will have settled) and pour it all over the ingredients.
5. Thicken and Serve: Stir everything together constantly. The sauce will bubble and begin to thicken almost immediately, thanks to the cornstarch and the heat of the pan. This should only take 1-2 minutes. Once the sauce has thickened to a glossy glaze that coats the beef and green beans, turn off the heat. Stir in the toasted sesame oil. Serve immediately.