Measure the flour, butter and sugar into a processor. Whiz until the mixture looks like breadcrumbs and then add the egg and water. Whiz again until it forms a ball.

Roll out the pastry thinly on a floured work surface until it is just a little bigger than the size of the tin. Line the tart tin with the pastry, letting the extra pastry hang over the sides of the tin. Prick with fork (but not all the way through to the bottom). Place on a baking sheet and then chill in the fridge for 30 minutes.

Preheat the oven to 400 deg F. Line with foil or cling film and fill with baking beans. Blind bake for 12-15 minutes in the preheated oven until pale golden brown.

Take out of the oven and remove the baking beans and paper. Carefully trim the excess pastry from the sides using a sharp knife. Return the empty pastry shell to the oven for another 5 minutes or until it is completely dry. Set aside to cool.