Lamb in sweet and sour sauce

1) Cut the lamb into thin slices.
2) Marinate the slices in 2tbsp of the cornflour and crushed black bean sauce for about 10 minutes.
3) Heat the rapeseed oil in a wok or saucepan and deep-fry the lamb slices for about 20 seconds, stirring to separate each piece.
4) When the slices are lightly coloured, remove with a perforated spoon and drain.
5) Pour off the excess oil, leaving about a tablespoon, add the ginger root, soy sauce, sherry, vinegar, sugar and remaining cornflour. Stir for about 1 minute.
6) Add the lamb slices and sesame oil and stir briefly before serving.