01 - Combine flank steak with cornstarch, soy sauce, and Shaoxing wine in a bowl. Toss well to coat 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 a boil. Add broccoli florets and blanch for 2 minutes. Drain well and set aside.
04 - Heat 1 tablespoon 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 but not fully cooked. Remove beef from pan and set aside.
05 - Add remaining 1 tablespoon oil to the pan. Sauté minced garlic and ginger for 30 seconds until fragrant.
06 - Return beef to the pan with blanched broccoli. Pour in sauce and stir-fry everything together for 2-3 minutes until sauce thickens and beef is cooked through.
07 - Serve immediately over steamed rice.