Prep the beef: Pat the beef dry. Toss with 1 tablespoon soy sauce and 1 tablespoon cornstarch until lightly coated.
Set aside while you prep the vegetables.
Mix the sauce: In a small bowl, whisk soy sauce, oyster sauce, rice vinegar, honey, broth, and 1 teaspoon cornstarch. Add chili-garlic sauce if using. Keep it nearby.
Heat the pan: Set a large wok or heavy skillet over medium-high to high heat.
Add 1 tablespoon oil and swirl to coat. You want the pan hot enough that a drop of water sizzles on contact.
Stir-fry the beef: Add beef in a single layer. Let it sear undisturbed for 30–45 seconds, then stir-fry 1–2 more minutes until mostly cooked with a little pink left.
Transfer to a plate.
Aromatics in: If the pan looks dry, add 1 teaspoon oil. Add garlic, ginger, and the white parts of the green onions. Stir for 20–30 seconds until fragrant.
Don’t let them burn.
Cook the veggies: Add broccoli and carrots first. Stir-fry 2 minutes. Add bell pepper, zucchini, and snap peas.
Cook 2–3 minutes more until crisp-tender. Keep them vibrant, not soft.
Sauce it up: Return the beef and any juices to the pan. Give the sauce a quick stir, then pour it in.
Toss for 1–2 minutes until the sauce thickens and coats everything.
Finish: Turn off the heat. Stir in sesame oil if using and the green parts of the onions. Taste and adjust with a splash more soy for salt, vinegar for brightness, or honey for balance.
Serve: Spoon over warm rice, quinoa, or cauliflower rice.
Garnish with sesame seeds and a squeeze of lime if you like.