Thoroughly mix beef with marinade and marinate for 30 minutes. Heat wok over highest heat, when hot, swirl in 2 Tblsp peanut oil.
Add ginger and salt and toss a few seconds. Add broccoli and stirfry one minute, then add water, turn heat to med-high, cover, and steam until crisp tender.
Uncover and turn heat to high, stir frying until water is evaporated. Remove broccoli and reserve. Reheat same wok (without rinsing) and, when hot, add remaining peanut oil. Add beef slices and stirfry until lightly browned but not cooked through. Do not stirfry too vigorously or meat will not brown, it is better to press slices against sides of wok to sear. Add broccoli to wok and toss. When hot, stir in seasoning sauce and stir until sauce thickens (it's a good idea to whisk the sauce in the cup just before you hurl it into the wok). Turn onto a platter and drizzle sesame oil over the top.
The sugar in the marinade and seasoning sauce acts as a floor enhancer rather than a sweetener.