Separate the egg white and yolk. Add 25ml cold water to the yolk and whisk until smooth.
Put the flour, butter, sugar and salt in the food processor. Or in a bowl if making by hand.
Pulse the food processor - or, if doing this by hand, rub together lightly between your fingers - until you have an even, slightly yellow crumb that resembles breadcrumbs or ground almonds.
Add the egg yolk and water mixture. Pulse again very briefly - or mix with a cutlery knife - until the pastry starts to clump.
Remove the pastry from the food processor / bowl and gather into a ball. Divide into cut into six equal pieces, then roll each piece in a ball.
Press each piece into a dic about 1-1.5cm thick (½ inch). If the pastry has become warm and soft, wrap each piece in clingfilm and place in the fridge to chill until firm but flexible.
Line the tarlet cases
When chilled to very firm, unwrap and roll out each piece to about 3mm (just under1/8 Inch) thick - the disc will about 15cm (5 inches) wide.
Use the pastry to line your tartlet cases, carefully lifting and pushing the pastry so that it sits flush in the corners with no gaps for air.
Use a small sharp knife to trim away the excess pastry then place the tins back into the fridge until hard.
Make the decorations
While the pastry case is chilling, cut out some decorative stars from the remaining pastry and set aside.
Fill and bake your mincemeat tart
When your pastry cases are firm, spoon the mincemeat into each case and level off. Make sure there’s about a ½ centermetre (1/4 inch) clear at the top of the cases so that they don’t bubble over when baking.
Top with the pastry stars.
Put the tartlet cases on a tray and place in the oven to bake for about 25 minutes minutes until gently golden. Keep a close eye in the final 10 minutes.
Allow the tartlets to firm up in the tin for 10 minutes, and then gently release from the tins and transfer to a wire rack to cool completely.