Add enough of the measured cold water for the mixture to come together and form a ball, then knead together until you have a workable dough.ĭivide the pastry dough into 8 equal parts, wrap each in clingfilm and refrigerate for a few hours until firm. Beat the egg, vinegar and salt together, then stir into the crumbed mixture, incorporating it quickly and thoroughly. To make the pastry, pulse the flour and butter together in a food processor until you have a uniform crumb with no lumps of butter within the flour.