For the dumpling dough, place the flour in a large bowl and add the lukewarm water a little at a time, mixing between additions until you have a soft dough. Turn the dough out onto a lightly floured surface and knead until it becomes smooth. This takes 7-10 minutes by hand. The dough should be soft but not wet to the touch - a bit like freshly made pasta. Cover and leave to rest for thirty minutes.
For the filling, put all the ingredients in a large bowl. Use a spoon to mix until smooth.
Uncover the dough and place on a flat, floured work surface. Sprinkle flour on the dough and cut into four equally sized pieces. Take one piece and roll into a sausage about 2cm/1in wide. Put the other three pieces back into the bowl and cover so that their surface doesn't go hard.
Cut off a thumb-sized piece of dough from the 'sausage'. Sprinkle with flour, so that it doesn't stick, then roll into a small disc about the thickness of a 50 pence piece. Make the middle of the dough disc slightly thicker to hold the weight of the filling.
Hold the disc in the palm of your hand and put a spoonful of the prawn filling in the centre of the disc. With your finger and thumb, nip the sides together, making a crescent shaped dumpling. There are many different ways to seal the dumpling, this is the easiest. Repeat with the rest of the dough and prawn mixture. Finished dumplings should be placed on a well-floured tray and kept covered with clingfilm.
Place the dumplings in a deep pot of boiling water and cook for 8-10 minutes, like cooking little ravioli. Small dumplings will take less time to boil. After three minutes, add 100ml cold water into the boiling pot, then the same again after another three minutes boiling. Boil for two minutes more, then drain and serve.