Put 150g plain flour and 75g unsalted butter in a bowl and rub together with your fingertips until it resembles breadcrumbs.
Mix in 50g icing sugar and a pinch of salt followed by 1 egg yolk. If the pastry feels too dry to form a dough, add 1 tbsp water. Shape the dough into a ball, flatten it out into a disc, wrap it in cling film, then chill for at least 30 mins before using in your recipes. You could try using it to make our apple & blackberry pies.