Prep the beef. Slice the steak thinly against the grain. In a bowl, mix 1 tablespoon soy sauce, 1 teaspoon cornstarch, 1 teaspoon oil, and a pinch of sugar. Toss in the beef and let it sit 10–15 minutes while you prep everything else.

Make the sauce. In a small bowl, combine 2 tablespoons soy sauce, 1 tablespoon oyster sauce, 1 teaspoon dark soy (optional), 1 tablespoon rice vinegar, 1 teaspoon brown sugar, 1/2 cup water, and 1–1.5 teaspoons coarsely ground black pepper. Stir in 1 teaspoon cornstarch until smooth.

Cook the noodles. Boil according to package directions until just al dente. Drain and rinse briefly under hot water to stop cooking and remove excess starch. Toss with a splash of oil to prevent sticking.

Prep the veg and aromatics. Slice the bell pepper and onion into thin strips. Trim snow peas or cut broccoli into small florets. Mince garlic and ginger. Slice scallions, separating whites and greens.

Heat the pan properly. Set a wok or large skillet over high heat until very hot. Add 1–2 tablespoons oil and swirl to coat.

Sear the beef. Spread beef in a single layer. Let it sear undisturbed for about 45–60 seconds, then stir-fry until mostly browned but not fully cooked through. Transfer to a plate. Don’t overcrowd; cook in two batches if needed.

Stir-fry the vegetables. Add a bit more oil if the pan looks dry. Toss in onion, bell pepper, and broccoli or snow peas. Stir-fry 2–3 minutes until crisp-tender.

Add aromatics. Push veggies to the side. Add garlic, ginger, and scallion whites. Stir 20–30 seconds until fragrant, keeping them from burning.

Combine beef and noodles. Return beef to the pan with any juices. Add the drained noodles and pour in the sauce. Toss vigorously over high heat for 1–2 minutes until everything is glossy and evenly coated. If it looks dry, splash in 1–2 tablespoons water.

Finish and serve. Turn off the heat. Drizzle 1 teaspoon sesame oil and scatter scallion greens. Taste and adjust with extra soy or black pepper. Serve hot.