In a medium bowl add 'marinade ingredients' (corn flour, dry sherry, sesame oil and reduced sodium soy sauce) and mix well.
Add the meat to the bowl and mix, making ensure all the slices are evenly coated. Set aside for 15 minutes so the beef can absorb the flavours.
Heat wok or pan, add oil, heat and add onion, garlic and ginger cook until soft but not browned.
Add thinly sliced beef with the marinade and cook over a high heat for 3 minutes.
Add the greens of your choice (example broccoli or snow peas) and green beans.
Add water to the wok and mix scrapping the sauce on the bottom of the wok.
Cook until the vegetables are just tender but retain their vibrant green colour (approximately 4 minutes).