In a bowl, combine sliced flank steak with soy sauce, Shaoxing wine, cornstarch, and sesame oil. Toss well and let stand at room temperature for 10 minutes while prepping other ingredients.

In a small bowl, stir together soy sauce, rice vinegar, chili paste, hoisin sauce, sugar, and beef broth. Set aside. In a separate little bowl, mix the cornstarch slurry.

Heat a wok or large skillet over high heat until smoking. Add 1 tablespoon oil and swirl. Spread half the beef in a single layer and let it sear undisturbed for 1 minute. Toss and cook 30 seconds more, or until beef is browned and reaches an internal temperature of 145°F (63°C). Remove to a plate. Repeat with remaining beef.

Reduce heat to medium-high. Add remaining 1 tablespoon oil, garlic, ginger, and dried chilies. Stir 15 seconds until fragrant, then add bell pepper and blanched broccoli. Stir-fry 2 minutes until crisp-tender.

Return beef (and any juices) to the pan. Pour in the sauce mixture and bring to a boil. Stir the cornstarch slurry, add it to the wok, and toss everything together for 1-2 minutes until sauce thickens and coats the beef.

Toss in scallion pieces, cook 30 seconds, then remove from heat. Top with sesame seeds and serve immediately over steamed rice.