Cut the pork fillet into thin slices and put it in the food processor. Whiz until minced. Put in a large bowl to combine with other ingredients.
Chop cabbage and carrot to small pieces and cut water chestnuts in half. Put in the food processor to whiz together until finely chopped. Add this to the minced pork mixture. Add soy sauce, oyster sauce, rice wine vinegar and salt-pepper. Stir until well mixed.
Place 1 heap teaspoon of pork filling onto dumpling wrapper, moisten edges with water and fold edges over to form a triangle shape. Make sure edge is closed by pinching with your fingertips and put in the steamer pot. Any leftover mixture can be frozen and used at another time.
Fill bottom pan with water add the lemon slices and place steamer on top to steam dumplings. Cover with the lid for about 10 to 15 minutes until the pastry wrapper is soft to taste. Sprinkle with sesame seeds and serve with your favourite dumpling dipping sauce.