To make the pastry by hand cream the butter and sugar together in a large bowl with a wooden spoon until pale and fully mixed.
Whisk the egg to break it up, then beat into the mixture.
Combine the flour and salt with the butter mixture.
Use your hands to squeeze the mixture together to form a dough.
To use the food processor put the egg, butter and sugar into a processor bowl and process for 10-15 seconds until well combined.
Tip in the flour and pulse until the mixture comes together.
For both methods, gather the pastry together in floured hands, knead lightly and place on a piece of cling film.
Use your fingers to form a rough ball shape then flatten with the palms of your hand.
Wrap over the clingfilm and refrigerate for at least 30 minutes and ideally 2 hours.
Unwrap the pastry from the fridge and dust the worktop with a little flour.
Roll the pastry out and line the tart tin. Trim the edges and lightly fork the base.
Chill for 20 minutes in the fridge or 10 minutes in the freezer.
Preheat the oven to 200 C / 400 F / 180 FAN / Gas 6 and place a rimmed oven tray into the oven to heat up.
Line the pastry with parchment and fill with baking beans.
Place the tin on a rimmed baking sheet and bake for 12 minutes. Carefully peel back the paper. If the pastry is set, then remove the paper and beans.
Cook for about 5 minutes more until the pastry is set and an even colour.
Remove from the oven to cool.