Slice the flank steak against the grain into 0.5 cm (1/4 inch) thick slices or 1-cm (1/2 inch) sticks. In a small bowl, combine with soy sauce, peanut oil, and cornstarch. Mix gently by hand until well coated and let marinate for 10 minutes.

In a medium bowl, combine chicken stock, Shaoxing wine, soy sauces, dark soy sauce, and brown sugar. Mix thoroughly.

In a large nonstick skillet, boil 1/4 cup water over medium-high heat. Add the broccoli, cover, and steam for about 1 minute, or until just tender. Transfer the broccoli to a plate and wipe out the pan.

Add the peanut oil to the skillet and heat until hot. Spread the marinated steak in a single layer and let sear undisturbed for 30 seconds, or until browned. Flip and cook for a few more seconds until lightly charred but still pink on the inside.

Stir in the minced garlic and ginger, cooking for a few seconds until fragrant.

Return the steamed broccoli to the pan. Stir the sauce again to ensure the cornstarch is completely dissolved and pour it into the skillet. Cook while stirring until the sauce thickens, about 1 minute.

Transfer everything to a plate and enjoy hot, either on its own or alongside rice or noodles.