Sift the dry ingredients, flour, 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 pour in your egg. Using a fork, mix in the egg into the flour. Add 2 tablespoons of ice-cold water and use your hands to bring the dough together. Add more water sparingly if needed.
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 cling film and refrigerate for 30 minutes minimum.
Pre-heat your oven to 180C/350F. Once chilled, let the dough sit at room temperature for 15 minutes until it is soft enough to roll. On a lightly floured surface, roll out the 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 the over-hang of your tart tin. Place the dough into the tart tin, and with your fingers, gently push the dough onto the sides of the tin into all the grooves. Using a sharp knife, cut the excess dough from the tin. Wrap excess dough in plastic wrap and set aside. Prick the pastry base all over with a fork and then line with greaseproof 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. Bake for a further 7 minutes until just golden. Set aside to cool whilst you make the filling.