Sift together the gluten free flour and xanthan gum, and whisk to combine well.
Beat together the butter, sugar, vanilla and lemon juice in a large bowl using a hand-held electric mixer (or use a stand mixer with the paddle attachment) just until combined and creamy. Don't beat for too long, it doesn't need to be fluffy, just well combined.
Beat in the egg. Don't worry if it starts to curdle.
Add in the dry ingredients in 2-3 additions, mixing until combined. You may need to mix in the last addition by hand. Tip the dough out onto the bench and give it a quick knead until smooth.At this stage you should be able to roll the dough out straight away, however if it is too soft, pop it into the fridge for 10-15 minutes until it firms up.
Dust a large sheet of non-stick baking paper with cornflour (cornstarch) or gluten free flour and place the dough on top. Roll out the dough to around 3mm thick, dusting the top with flour only if needed. Slide the paper and dough onto a baking sheet and refrigerate until firm (10-15 minutes).
Heat oven to 180°C (350°C) and grease a 12-hole muffin tin or tart tin with oil spray or butter.
Cut out circles of dough using a large round biscuit cutter. Gently place them into the muffin pan. If they're still too cold and firm, let them sit on the top of the pan for a minute to soften first, then gently ease them in using the pads of your fingertips.Re-roll the dough as necessary.
Fill the pies with fruit mince, almost to the top.
Cut small shapes from the remaining dough and place on top of the pies.If you don't have small enough cutters, free-hand cut the shapes with a knife, or just crumble some of the extra dough over the tops.
(Optional) Make an egg wash by beating the extra egg with a fork, then brush onto the tops of the pies using a pastry brush.
Bake for 15-20 minutes. The exact baking time will depend on how deep your mince pies are. When done, they should be lightly golden on top and around the edges.
Cool the pies in the pan for 5-10 minutes, until firm enough to handle. Carefully remove each pie and place them onto a wire rack to cool, or serve warm.
Notes
If you would like to make mince pies with fully covered tops, you will need to make 1.5x this recipe so you have enough dough to cover the tops.Gluten free flour - I use my homemade gluten-free flour blend, however you can use your own favourite homemade or store bought gluten-free all-purpose flour blend. Please note that as different gluten-free flour blends contain different ingredients, they may give slightly different results. Omit the xanthan gum if using a gluten free flour blend that contains a gum ingredient (check the ingredients list).To freeze the unbaked pies - Prepare the pies as directed but omit the egg wash. Place the muffin tray in the freezer and freeze the pies until solid, then carefully pop them out of the tray and transfer them to an airtight container or freezer bag. Freeze until needed (up to 3 months), then thaw at room temperature and bake as usual.To freeze the baked pies - Bake and cool the pies to room temperature, then place into an airtight container or freezer bag, separating the layers with baking paper. Freeze for 2-3 months. Thaw at room temperature.