Remove your pastry from the freezer. It should be firm now. If it still feels sticky, then put it back in. You'll use ⅔ of the dough to form the cases of the mince pie and the remaining ⅓ to form the lids.
Take a piece of dough the size of a ping pong ball and press into your muffin tin. The pastry doesn't need to come all the way up to the top. Repeat this until ⅔ of the pastry dough has been used.
Spoon the mincemeat evenly between the cases.
Finally, take half the amount of dough as before and press it into a rough circle that's big enough to cover your pies and place on top. No need to seal with water or egg. If there was any dough left up the sides of the muffin hole, I folded it down to meet the lid. Repeat for the remaining mince pies.
I now like to put them back in the freezer for 20 minutes. Help to make sure the pastry is flaky.
Preheat your oven to 200°C/180°C fan.
Remove from the freezer and brush the tops with beaten egg and a sprinkle of demerara sugar.
Bake for 20-25 minutes until golden. Leave to cool in the tin for 5 mins, then remove to a wire rack. To serve, lightly dust with the icing sugar. Easiest to do this using a sieve.