Put the flour and 225g/8oz of the butter in a bowl. Cut the butter into the flour using two knives until it resembles large crumbs. Gradually add the chilled water, stirring with a knife and pressing together until a rough dough forms.
Turn onto a lightly floured work surface and roll into a rectangle. The dough is crumbly and hard to manage at this point. Fold the dough and re-roll several times. Wrap the pastry in cling film and refrigerate for 30 minutes, then fold and re-roll a few more times. Wrap again in cling film and refrigerate for another 30 minutes.
Preheat the oven to 190°C/375°F/Gas mark 5. Roll the pastry until 3mm/1⁄2in thick. Cut into 8 x 10cm/4in rounds.
Peel, core and slice the apples. Arrange in a spiral on the pastry. Sprinkle well with the caster sugar, and dot with the remaining butter. Bake on greased baking trays for 20–30 minutes until the pastry is crisp and golden. Serve warm with cream or ice cream.