Combine the beef, soya sauce, garlic and corn flour and leave to marinate for 15 minutes
Heat a wok or large frying pan over high heat.
Add half the oil and stir-fry the beef in two batches until brown. Set aside.
Reduce the heat slightly, add the remaining oil and fry the leeks until soft.
Add the broccoli and cook until just tender.
Stir in the beef, season to taste and heat through.
Serve with noodles or rice.
For a delicious nutty flavour, drizzle with 5 ml sesame oil before serving.