Make the pastry - To a large mixing bowl add plain gluten free flour, xanthan gum, sugar and salt. Mix well.
Add your cold cubed butter and rub in with a fork until it starts to look like breadcrumbs. Add the egg and mix in using a table knife.
Add water 1 tablespoon at a time and mix well until it starts to form a dough.
Turn out onto a floured surface and knead until smooth. Wrap in clingfilm and leave in the fridge for atleast an hour.
After an hour preheat your oven to 180°C and remove the pastry from the fridge. Roll out on a floured surface until it's about 1cm thick.
Cut out 12 circles (larger than your cupcake tin) and press the circles into your cupcake tin, ensuring that you press the pastry up the side of the tin.
Spoon around 1 tablespoon of mincemeat into each of the unbaked pastry cases.
Make the frangipane filling. Whisk the butter and sugar until combined. Add the egg and mix again. Mix in the flour and ground almonds.
Spoon the frangipane on top of the mince pies and level with a knife. Top with flaked almonds. Bake in the oven for around 25 minutes, until golden brown. Dust with icing sugar.