Slice the beef thin. Freeze the steak for 15–20 minutes to firm it up. Slice into thin strips against the grain. Thin slices cook fast and stay tender.

Marinate the beef. In a bowl, mix soy sauce, cornstarch, sugar, rice vinegar or sherry (if using), and sesame oil. Toss in the beef until coated. Let it sit for 10–20 minutes while you prep the vegetables.

Mix the sauce. In a small bowl, whisk soy sauce, oyster sauce, hoisin (if using), rice vinegar, sugar or honey, broth, and cornstarch until smooth. Set aside.

Prep the vegetables. Cut them into bite-size pieces. Keep quick-cooking veggies (snow peas, peppers) separate from sturdier ones (broccoli, carrots) so you can add them in stages.

Heat the pan properly. Use a large wok or wide skillet. Heat 1–1.5 tablespoons of oil over high heat until it shimmers. A hot pan prevents steaming and helps with browning.

Sear the beef in batches. Add half the beef in a single layer. Let it sear undisturbed for 30–45 seconds, then stir-fry until just browned, 1–2 minutes more. Remove to a plate. Repeat with remaining beef, adding a little more oil if needed.

Stir-fry the vegetables. Add another splash of oil. Toss in the onion, carrots, and broccoli. Stir-fry 2–3 minutes until bright and slightly tender. Add bell pepper and peas; cook 1–2 minutes more. You want crisp-tender, not soft.

Add aromatics. Push veggies to the sides, add a little oil to the center, then add garlic, ginger, and chili (if using). Stir 20–30 seconds until fragrant. Don’t burn them.

Bring it together. Return beef and any juices to the pan. Give the sauce a quick stir (cornstarch settles) and pour it in. Toss everything for 1–2 minutes until the sauce thickens and coats the beef and vegetables.

Finish and serve. Taste and adjust salt, sweetness, or acidity. Remove from heat. Sprinkle with scallions and sesame seeds. Serve over hot rice or noodles with a squeeze of lime if you like a fresh pop.