Have you tried this fish recipe yet?
Sift the flour onto a surface. Grate the cooked, peeled potatoes into it. Add butter flakes, season with salt and maybe some freshly grated nutmeg. Rub the ingredients together with your hands, press into a ball and leave to cool for 1 hour, preferably overnight, with the lid closed.
Dust the work table with a little flour, roll out the dough on it and cut it out to the size of the fish pieces.