Begin by slicing the flank steak against the grain into thin strips for maximum tenderness. In a mixing bowl, combine the beef with soy sauce, peanut oil, and cornstarch, ensuring the meat is thoroughly coated. Let it marinate for about 10 minutes while you prepare the other ingredients.

In a separate bowl, mix together the chicken stock, Shaoxing wine, soy sauce, dark soy sauce, brown sugar, and cornstarch. Stir until the cornstarch is fully dissolved.

Fill a skillet with a small amount of water and bring it to a boil over medium-high heat. Add the broccoli florets and cover the skillet for about 1 minute to steam.

Return the skillet to the heat, adding a drizzle of peanut oil. Once hot, spread the marinated beef in a single layer, allowing it to sear for about 30 seconds. Flip and cook for an additional minute.

Stir in the minced garlic and ginger, cooking for about 30 seconds until fragrant.

Return the steamed broccoli to the skillet and pour in the prepared sauce. Cook everything together for about 1 minute, stirring until the sauce thickens and coats the beef and broccoli evenly.