Crush the tomatoes and place in cheese cloth covered sieve on a collection bowl overnight in the fridge to allow the clear water from the tomatoes to collect. You can speed up the process by squeezing them through the cloth.
Add 8-10 egg yolks to 250 grams of flour with a dash of salt and knead or use food processor until dough forms. Roll out to form sheets.
Kill the crayfish by first chilling it down in a freezer or ice slurry of -1C then placing a knife lengthways through the shell behind the eyes.
Then boil the crayfish for 6 minutes.
Cut the crayfish tail into chunks and separate leg and shell meat along with the crayfish mustard (stomach contents) and set aside.
Add crayfish offcuts and mustard to blender with 1 small fillet of fish, lemon zest and a quarter lemon squeezed. Add white of one egg and 50 mls of cream and blend to form a paste. If too thick add more cream. Season with salt and pepper to taste.
Add filling to piping bag and pipe a 1cm line of mixture down the pasta sheet. Fold the pasta sheet over and seal the edge and ends. Pinch the pasta with your fingers to form 1.5cm long packets of filling. Using a fluted pasta cutter, cut the edge and in between the parcels to form rectangular pockets. Then fold the flat edge up to bond with ends of the parcel and flatten the bottom so they sit upright. Poach in boiling water for 3 or 4 minutes until they float to the surface signalling they are cooked.