Slice the beef flank steak into thin strips, combine in a bowl with Shaoxing wine, salt, black pepper, and cornstarch. Mix to coat and marinate for 15 minutes.

In a separate bowl, whisk together chicken broth, soy sauce, additional Shaoxing wine, rice vinegar, sesame oil, sugar, minced garlic, and an extra teaspoon of cornstarch. Set aside.

Heat the peanut oil in a large skillet over medium-high heat. Add the marinated beef strips in a single layer; cook undisturbed for about 1 minute until browned, then flip and cook for another minute.

Transfer the beef to a plate, reduce the heat to medium, and pour the sauce mixture into the skillet. Stir until the sauce thickens, about 1-2 minutes.

Return the beef to the skillet, tossing well in the sauce, and cook for another minute to absorb the flavor.

Remove from heat, serve garnished with toasted sesame seeds, and enjoy over steamed rice.