You can prepare this dough in your food processor. Alternatively, you can prepare it by hand.

Mixing the dry ingredients: In a large bowl, combine the flours, sugar, and a pinch of salt. Be sure to sift the icing sugar well to avoid lumps.

Incorporating the butter: Add the cold butter cubes to the dry ingredients. Using your fingertips, work the butter into the flour until the mixture resembles coarse sand.

Add the egg; Make a well in the center of the mixture and crack the egg into it. Gently mix with your fingers or a spatula until you obtain a smooth dough. If the dough is too dry, add one to two tablespoons of cold water.

Resting the dough: Form the dough into a ball and wrap it in plastic wrap. Let it rest in the refrigerator for at least 30 minutes. This resting time is essential for the dough to be easier to roll out.

Roll out and bake the pastry: Preheat your oven to 180°C (350°F). Remove the pastry from the refrigerator and roll it out on a lightly floured work surface (using gluten-free flour). I personally roll it out between two sheets of cling film. Then place it in a tart tin or cut out circles for tartlets. Prick the base of the pastry with a fork to prevent it from puffing up during baking (this is optional if you are baking the tart directly with the filling).

If you're not baking the pastry with the filling, blind bake it. To blind bake: Cover the pastry with parchment paper and baking weights (or dried beans). Blind bake the pastry for about 15 minutes. Then remove the paper and weights and bake for another 5 to 10 minutes until the pastry is golden brown.