Start by slicing the flank steak against the grain into thin strips. In a mixing bowl, combine the beef with soy sauce, peanut oil, and cornstarch. Allow it to marinate for about 10 minutes.

In a separate bowl, whisk together the chicken stock, Shaoxing wine, dark soy sauce, and brown sugar for the sauce.

Bring a nonstick skillet filled with water to a boil. Add the broccoli florets and steam for about 1 minute until tender but crisp. Set aside.

In the same skillet, heat peanut oil over high heat. Add the marinated beef and cook for 2-3 minutes until browned on one side, then flip and cook for another 2 minutes.

Stir in minced garlic and ginger shortly before the beef is fully cooked, cooking for about 30 seconds.

Return the steamed broccoli to the skillet, pour the sauce over everything, and stir gently. Cook for an additional 2-3 minutes while the sauce thickens.