Marinate beef with soy sauce and cornstarch for 15 minutes.
Mix beef broth, soy sauce, oyster sauce, cornstarch, sugar, and sesame oil to make sauce.
Heat oil, sear beef 30 seconds, then stir-fry until browned. Transfer to plate.
Add oil, garlic, and ginger; stir-fry 30 seconds.
Add broccoli and water, cover, steam 1-2 minutes until bright green and crisp-tender. Return beef, add sauce, cook 30-60 seconds until thickened. Serve over rice.
Notes
Use high heat for stir-frying to prevent sticking and ensure quick cooking.