Sift the dry ingredients, flour, powdered icing sugar and salt into a large bowl. Add the cold, cubed butter into the flour and rub the butter and flour together between your fingers until it resembles a bread crumb consistency.
Make a well in the flour's centre, and using a fork, mix the egg into the flour. Add 2 tablespoons of ice-cold water and use your hands to bring the dough together.
Turn the dough out onto a lightly floured surface and press the dough just a couple of times to gather all the crumbs into a ball. Then shape the dough into a disc lightly with your hands. Wrap the dough a couple of times with plastic wrap and refrigerate for 30 minutes minimum.
Preheat your oven to 180°C (350°F). Once chilled, let the dough sit at room temperature for ten minutes and then on a lightly floured surface, cut the disc into six even pieces. Roll out each piece of dough until it’s the thickness of a coin.
Ensure the dough is rolled out large enough to cover the base, the sides and enough for over-hang of your tartlet tin. Place the dough into the tart tin and with your fingers gently press the dough up the sides of the tin into all the grooves. Using a sharp knife, cut the excess dough from the tin. Repeat with the remaining dough and tart tins.
Prick the pastry base all over with a fork and then line each tart base with parchment paper and fill with pie weights all the way up the sides.
Bake for 15 minutes, then remove the parchment paper and pie weights and return the pastry back to the oven for a further 15 minutes until golden brown.
Remove the six tarts from the oven and allow to cool fully.