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 and view the full Food safety at home video.