Begin by thinly slicing flank steak against the grain. In a bowl, combine the sliced beef with soy sauce, peanut oil, and cornstarch. Allow it to marinate for about 10 minutes.

While the beef marinates, whisk together chicken stock, Shaoxing wine, soy sauce, dark soy sauce, brown sugar, and cornstarch in a bowl until smooth.

Bring about an inch of water to a boil in a skillet. Add broccoli florets to steam for about 1 minute until bright green and just tender. Transfer the broccoli to a plate.

In the same skillet, heat a splash of peanut oil over high heat. Add marinated beef in a single layer and let it sear for about 2 minutes until browned, then flip and cook for another minute.

Add minced garlic and ginger to the skillet, sautéing quickly for about 30 seconds until fragrant.

Return the steamed broccoli to the skillet, pour in the prepared sauce, and stir to coat. Cook for another minute until the sauce thickens.