170g plain flour
100g cold unsalted butter
1 tbsp caster sugar
1 large free-range egg yolk
1. Sift 170g plain flour and a pinch of salt into a bowl. Rub in 100g cold unsalted butter, cut into cubes, with your fingers until you have a crumble-like mixture.
2. Stir in 1 tbsp caster sugar, then add 1 large free-range egg yolk and mix quickly with a palette knife. Add 1-2 tbsp cold water, a little at a time, mixing with the knife until the mixture is drawn together into a dough.
3. Press into a ball, then wrap in cling film and chill for at least 10 minutes.