Marinate the sliced beef in soy sauce and one tablespoon of cornstarch for about 15 minutes.
This helps to tenderize and flavor the beef.
Heat a large skillet or wok over high heat, then add the olive oil.
Once hot, add the beef, cooking it until browned outside but still pink inside. This should take about 3-4 minutes.
Remove from pan and set aside.
In the same skillet, add sesame oil and then the garlic and ginger.
Stir for about 30 seconds or until fragrant.
Add broccoli florets with a splash of water, cooking until bright green and tender-crisp, roughly 3 minutes.
Return the beef to the pan with the broccoli.
In a small bowl, mix the remaining cornstarch with water to create a slurry.
Pour into the skillet with the beef and broccoli.
Add oyster sauce and stir everything to combine and thicken, about 1-2 minutes.