01 - Combine flank steak with cornstarch, soy sauce, and Shaoxing wine in a bowl. Toss thoroughly and let marinate for 10 minutes.
02 - Whisk together oyster sauce, soy sauce, dark soy sauce, brown sugar, cornstarch, beef broth, and sesame oil in a separate bowl until smooth.
03 - Bring a pot of water to boil. Blanch broccoli florets for 2 minutes, then drain and set aside.
04 - Heat 1 tbsp vegetable oil in a large skillet or wok over high heat. Add marinated beef in a single layer and sear for 1-2 minutes until browned. Remove beef and set aside.
05 - Add remaining 1 tbsp oil to the pan. Sauté garlic and ginger for 30 seconds until fragrant.
06 - Return beef to the pan, add blanched broccoli, and pour in the sauce. Stir-fry for 2-3 minutes until sauce thickens and beef is cooked through. Serve immediately with steamed rice.