Slice the flank steak against the grain into 1/4-inch thick pieces and marinate with soy sauce, peanut oil, and cornstarch for 10 minutes.

Prepare the sauce by whisking together chicken or beef stock, Shaoxing wine or dry sherry, dark soy sauce, and brown sugar until dissolved.

Steam broccoli florets in boiling water for 1 minute, then transfer to icy water to preserve color. Drain and set aside.

Heat skillet over medium-high and add peanut oil. Sear marinated beef for 2-3 minutes until browned but still pink inside.

Add minced garlic and ginger, sauté for 30 seconds.

Add steamed broccoli and sauce to skillet, cook for 1 minute until sauce thickens.

Serve hot over rice.