Thinly slice the flank steak against the grain to about 1/4 inch thickness. Marinate with soy sauce and baking soda for 30 minutes.

Coat the marinated beef with cornstarch until well coated.

Heat vegetable oil in a large skillet or wok over medium-high heat until shimmering.

Stir-fry the beef in batches for 2–3 minutes until browned and crispy. Set aside.

In the same skillet, stir-fry minced ginger and garlic for 30 seconds. Add soy sauce and brown sugar; stir until dissolved and slightly thickened, about 2-3 minutes.

Return beef to the skillet and stir to coat with sauce. Cook for an additional 1–2 minutes until heated through.

Serve hot with fluffy rice and stir-fried vegetables.