Mix the marinade ingredients together (soy, oil and corn flour). Put the meat into a bowl and pour the marinade over. Use your hands to make sure the meat is fully coated and put into the fridge for half an hour.
Take a wok and a small saucepan. Add groundnut oil to both and put them on high heat. When the oil starts to smoke in the saucepan add the ginger. Stir and sauté for about a minute, then add the vegetables and soy sauce. Allow to come to the boil and then add the water and stir fry the vegetables in the steam for 5 minutes. At this point the oil in the wok should be really smoking.
Add the beef to it and stir fry, keeping the meat moving at all times, for around 4 minutes. Then transfer the vegetables into the wok from the saucepan and let the whole lot bubble for about 2 minutes. Serve straight away with rice.
For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home.