Beef and Broccoli with Oyster Sauce

1 lb. flank steak
1 tbsp. cornstarch
1/4 tsp. salt
1/4 tsp. sugar
1/8 tsp. baking soda
2 c. sm. broccoli florets
3 tbsp. peanut oil
2 garlic cloves, minced
1 sm. yellow onion, cut into 1-inch dice

Sauce:
2 tbsp. oyster sauce
2 tbsp. soy sauce
1 tsp. peanut oil
1 tsp. cornstarch
1/2 tsp. sugar
1/8 tsp. freshly ground pepper

Cut steak across grain into strips 3 inches long and 1/4-inch thick. In a bowl, stir together cornstarch, salt, sugar, baking soda, and 2 tbsp. water. Add beef and stir until well-mixed. Let stand at room temperature for 30 minutes.

Meanwhile, make the sauce: In a bowl, combine oyster sauce, soy sauce, peanut oil, cornstarch, sugar, pepper, and 2 tbsp. water. Set aside.

Bring a saucepan 3/4 full of water to a boil over high heat. Add broccoli florets and blanch until just tender, 3 to 4 minutes. Drain, rinse until running cold water until cool, and drain again. Set aside. Remove beef from bowl and pat dry with paper towels. In a wok or large, deep saute pan over high heat, warm 2 tbsp. peanut oil until very hot. Add beef and stir-fry until just opaque, 3 to 4 minutes. Using a slotted spoon, quickly transfer beef to a sieve placed over a bowl to drain. Wipe out pan with paper towels and reheat over high heat. Add remaining 1 tbsp. oil and heat until very hot. Add onion and stir-fry until tender, about 5 minutes. Add garlic, and stir-fry until golden, about 30 seconds more. Add sauce to pan, stir, and bring to a boil. Immediately add beef and broccoli and stir-fry until sauce thickens and beef is heated through, about 3 minutes. Transfer beef and broccoli to warmed bowl and serve.