Slice beef thinly against the grain
Marinate beef with soy sauce, cornstarch, and a little oil
Cut broccoli into florets
Blanch broccoli in boiling water for 1 to 2 minutes
Drain broccoli and set aside
Mix sauce with soy sauce, oyster sauce, garlic, ginger, sugar, and water
Heat oil in a skillet or wok over medium-high heat
Stir-fry beef until browned
Remove beef from the pan
Stir-fry garlic and ginger briefly
Add broccoli to the pan
Pour in the sauce
Return beef to the pan
Toss everything until coated and heated through
Serve hot over rice