Make the Sauce:
In a small bowl, whisk together soy sauce, beef broth, brown sugar, cornstarch, oyster sauce, and rice vinegar. Set aside.
Prepare the Broccoli:
Bring a pot of water to a boil. Blanch broccoli for 1–2 minutes until bright green and slightly tender. Drain and set aside.
Sear the Beef:
Heat oil in a large skillet or wok over high heat. Add sliced beef and stir-fry for 2–3 minutes until browned. Remove from pan and set aside.
Cook Aromatics:
In the same pan, add garlic and ginger. Stir for 30 seconds until fragrant.
Combine Everything:
Add the sauce to the pan and bring to a gentle simmer. Return beef and broccoli, tossing to coat evenly in the sauce. Stir-fry for another 2–3 minutes until thickened and glossy.
Serve:
Serve hot over rice or noodles. Garnish with sesame seeds or chopped green onions if desired.