Half-fill a saucepan with water and bring to the boil. Add the lamb, cover and boil for minutes over moderately high heat. Remove from the heat and drain. Put the lamb on chopping board and cut it, including the skin into cubes. Arrange the cubes, skin side down on the bottom of a heatproof basin. Sprinkle over the peppercorns and ginger and spoon over the pickle.

Combine the soy sauce and wine or sherry and pour over the meat. Arrange the onions on top. Cover with a circle of greaseproof or waxed paper about 10 cm (4 in) wider than the rim of the basin and greased with butter. Cut out a circle of foil the same size, pleat the two and tie securely around the basin with string. Put the basin in a large saucepan and pour in enough boiling water to come about two-thirds of the way up the sides of the basin. Cover the pan and place over low heat. Steam for 2 1/2 hours, adding more boiling water if necessary

When the lamb has finished steaming, lift the basin out of the water and remove the foil and paper circles. Transfer the mixture to a warmed serving dish and serve at once.