Slice the flank steak thinly against the grain and marinate it with soy sauce, peanut oil, and 1 tbsp of cornstarch for 10 minutes.

Prepare the sauce by mixing chicken or beef stock, Shaoxing wine, dark soy sauce, brown sugar, and remaining cornstarch in a separate bowl.

Steam the broccoli florets by boiling water in a skillet, adding broccoli, and covering for 1 minute.

Sear the marinated beef in a hot skillet for 2-3 minutes until browned, making sure not to overcrowd.

Add minced garlic and ginger to the cooked beef, stir for 30 seconds, then add the steamed broccoli and prepared sauce.

Mix well and cook for an additional minute until the sauce thickens, then serve hot.