01 - Combine flank steak slices with 1 tbsp soy sauce, 1 tsp cornstarch, and 1 tsp sesame oil in a medium bowl. Toss to coat evenly and let rest for 10 minutes.
02 - Whisk together oyster sauce, 2 tbsp soy sauce, Shaoxing wine, sugar, 2 tsp cornstarch, and 1/3 cup plus 1 tbsp water in a small bowl. Set aside.
03 - Heat 1 tbsp vegetable oil in a large wok or skillet over medium-high heat. Add marinated beef in a single layer and stir-fry for 1 to 2 minutes until browned but not fully cooked. Transfer beef to a plate.
04 - Add the remaining 1 tbsp vegetable oil to the wok. Stir-fry minced garlic and grated ginger for about 30 seconds until fragrant.
05 - Add broccoli florets and 2 tbsp water to the wok. Stir-fry for 2 to 3 minutes until broccoli is bright green and just tender.
06 - Return the beef to the wok, pour in the prepared stir fry sauce, and toss to combine. Cook for 2 to 3 minutes until the sauce thickens and coats the beef and broccoli.
07 - Serve hot immediately, optionally accompanied by steamed rice.