Shell the prawns, cut them in half lengthways and remove the black intestinal vein.
Wash and dry.
Heat the oil in a wok until it begins to smoke, then add the ginger to flavour the oil.
Remove after 30 seconds.
Combine 2 tablespoons cornfour, the salt, pepper, wine and egg white.
Toss the prawns in this mixture.
Add them to the hot oil, turning and stirring until they change colour.
Remove from the wok with a slotted spoon.
Pour off all but 1 tablespoon of oil from the wok.
Reheat, then add the managetout and water chestnuts and stir-fry until they change colour.
Return the prawns to the wok.
Blend the remaining teaspoon of cornflour with the water and stir it in.
Add the sesame oil and spring onions.