Heat half the oil in a large frying pan or wok on high. Stir fry beef in batches for 1-2 mins until brown. Remove each batch of beef from pan and set aside. Heat remaining oil in same wok on high. Stir fry onion for 3-4 mins until soft.
Add spring onion, garlic and ginger and cook 1-2 mins until fragrant. Return beef to pan. Whisk together the remaining ingredients and add to beef and stir fry for 1 min until sauce has thickened slightly.
Serve stir-fried beef with steamed rice or noodles.