For the sweet-crust gluten-free pastry:
75g unsalted butter at room temperature
75g icing sugar
In a food processor combine the cubed butter, icing sugar and egg. In a bowl stir the flours together with the xanthan gum and add to the butter mixture.
75g tapioca starch
50g potato starch
125g white rice flour
1/2 tsp xanthan gum
Pulse until the pastry forms a ball. Flatten the dough into a disc and wrap in plastic wrap - chill in the fridge for at least 30 minutes. This can be made ahead of time and left in the fridge until required.
Place the disc of dough between two pieces of plastic wrap and roll out. The dough may be resistant to stretching but keep rolling until you reach a thickness of roughly an 1/8th of an inch. Drape the dough over a 20-22cm loose-bottomed cake or tart tin. You may have to patch the dough a little around the sides and top edges but it will look great in the end. You can even leave the top edge looking uneven which adds to the character -making it look a little more rustic. Preheat the oven to 200°C. Fill the tart crust and bake for 15 minutes, and then turn down the heat to 180°C/350°F and bake for at least 30 minutes.
For Tarts with liquid/Custard fillings:
Prick the base with a fork and chill in the fridge for 15 minutes THEN preheat the oven to 190°C while you add the filling to the tart.
Remove the pastry from the fridge and prepare to weight the pastry for baking. Cut enough parchment paper so that it will cover the base of the pastry and so that it can be filled with baking beans (I use rice grains which is often a cheaper option than buying baking beans). Try to evenly distribute the weight so that it reaches the outer edges of the pastry base to prevent rising.
Bake the pastry for 10 minutes and remove paper and baking beans/rice. If the fork marks reveal the tin base then brush the pastry with a beaten egg to help seal it. If given the egg-wash treatment then return the pastry to the oven for a further 10 minutes.
Add the filling and return to the oven.