Rub in butter, add vinegar, then add enough water to form a soft dough. Knead well.
Mix all the filling ingredients together.
Divide the filling and the dough into equal number of portions.
Flatten each portion of dough as thinly as you can on the palm of your hand, put a portion of filling on end of the dough and fold over like crescents or half moon shapes.
Seal and pinch the edges together.
Place each dumpling on a piece of wax paper and steam for half an hour or till the dough is cooked.
Serve on the wax paper with sweet and sour sauce.
Each person removes the paper before eating the dim sim or dumpling.