Place your flour and xanthan gum into a large bowl and mix. Make sure your butter is cold, cut it into small cubes and rub it in until the mixture resembles breadcrumbs.
Stir in your caster sugar.
Beat your 2 eggs together in a separate bowl and gradually add them. Use a fork to bring it all together. It should form a ball and not be very crumbly. The ball might be a tiny bit sticky but very minimally.
Wrap your pastry in cling film. Place in the fridge for 30 minutes (or longer). Don't skip this part - it's very important!
Preheat your oven to 160C Fan / 180C and prepare a baking tray with non stick baking paper.
Remove your pastry from the fridge – if your dough feels really firm when you take it out, leave it out at room temperature before rolling it. If it's too cold when you roll it, it will crack so ensure its warmed up a bit!
Lightly flour your rolling pin. Roll out the dough to a rectangle, about 2mm thick. Cut as many 4x3in rectangles out of your pastry as you can. Put them to one side while you reroll your pastry to cut out more rectangles.
Brush around the border of half of your rectangles with some of your beaten egg mixture, then add a tablespoon or so of mincemeat. Spread it out, leaving a half inch border around the edge.
Using a fork, prick some holes in the remaining rectangles (which will allow steam to escape when baking).
Press these rectangles on top of the mincemeat, the egg should seal them together but then additionally use a fork to push down and seal the edges even more.
Brush the top of each with egg wash and bake in the oven for 20-25 minutes until golden. Remove from the oven and allow to cool.
If you want to make the icing, place your icing sugar in a bowl and add a little water at a time and your extract until you have a very thick icing. You'll probably only need a couple of tablespoons at most. Make sure you mix it thoroughly so you don't add too much. If it does become too thin, just add more icing sugar to correct this.
Once cooled, drizzle the icing onto each pop tart. Add a few festive sprinkles and repeat until you’ve decorated all of your pop tarts. Allow to set and enjoy.