Mix the sauce ingredients (oyster sauce, soy sauce, sesame oil, sugar, and stock) in a bowl and set aside
Heat oil in a wok over medium heat, add broccoli and stir-fry for 4 minutes until just tender
Add ginger and garlic, cook for 30 seconds, then remove and set aside
Add more oil and crank the heat up, sear the beef in batches for about 3-4 minutes until browned
Return broccoli, garlic and ginger to the wok
Pour in the sauce and toss to coat, then stir through the cornstarch slurry
Let it bubble for a minute until glossy and thickened
Serve hot over steamed rice, topped with spring onion if desired
