Cut the steak across the grain into strips 3 inches long and 1/4 inch wide.
In a bowl, stir together the 1 Tbsp cornstarch, 1/4 tsp salt, 1/4 tsp sugar, the baking soda, and 2 Tbsp water. Add the beef and stir until well mixed. Let stand at room temperature for 30 minutes.
In another bowl, combine the oyster sauce, both soys, 1 tsp oil, the remaining 1 tsp cornstarch, the remaining 1/2 tsp sugar, white pepper to taste, and 2 Tbsp water, st aside. Bring a sauce pan 3/4 full of water to boil, and add broccoli florets, blanch until just tender 3-4 minutes. Drain, rinse under cold water until cool, then drain again. Set aside.
Remove the beef from the bowl and pat dry with paper towels. In a wok or large, deep saute pan over high heat, heat 2 Tbsp of peanut oil until very hot. Add the beef and stir fry until opaque, 3-4 mintues. Using a slotted spoon, quickly transfer the beef to a sieve placed over a bowl to drain.
Wipe out the pan with paper towels and reheat over high heat. Add the remianing 1 Tbsp oil and heat until very hot. Add garlic, and ginger and stir fry just until golden brown, 15-20 sec. Using slottted spoon, lift out the ginger and garlic and discard. Add the onion to the pan and cook until just tender, about 5 minutes. Pour in the rice wine and deglaze the pan stirring to dislodge any brown bits on the bottom. When the wine has evaporated, add the sauce, stir, and bring to a boil. Immediately add the beef and broccoli and stir fry until the sauce thickens and the beef is heated through, about 3 minute Transfer to a warm bowl and serve.