01 - Combine flank steak with cornstarch, soy sauce, and Shaoxing wine in a bowl. Toss thoroughly to coat and set aside to 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 and fully combined.
03 - Bring a pot of water to a rolling boil. Add broccoli florets and blanch for 2 minutes until bright green and slightly tender. Drain well and set aside.
04 - Heat 1 tablespoon vegetable oil in a large skillet or wok over high heat until smoking. Add marinated beef in a single layer and sear for 1-2 minutes until browned but not fully cooked through. Remove beef from pan and set aside.
05 - Add remaining 1 tablespoon oil to the hot pan. Sauté minced garlic and ginger for 30 seconds until fragrant, being careful not to burn.
06 - Return beef to the pan along with blanched broccoli. Pour in the sauce mixture and stir-fry everything together for 2-3 minutes until sauce thickens and coats all components evenly and beef is cooked through.
07 - Transfer to a serving platter and serve immediately while hot, accompanied by steamed white rice.