Sieve the flour into a large mixing bowl and add the butter. Rub the butter and flour between your fingers until the mixture looks like crumbs. Stir through the egg yolk and sugar and squish everything together in the bowl to create a dough. This could take a bit of work from the crumb stage. Add the chocolate chips and spread evenly throughout. Once it has begun to come together, tip out on to your work surface and form it into a flattened round puck shape, and wrap and chill for 30 mins.

Heat the oven to 170C/150C fan/gas 3. Line 2 baking sheets with baking parchment.

Roll out the dough in between two sheets of baking parchment until its 1cm thick. Remove the top sheet of parchment, and cut into 14 rounds with a 7cm round biscuit cutter. Re-roll any offcuts to make the most from your dough. Carefully transfer the rounds to your baking sheets using a palette knife or spatula, leaving some space in between them. Sprinkle each one with a little sugar. Bake in the oven for 15-20 mins or until lightly golden. Remove from the oven and allow to cool for 10 mins before transferring to a wire rack to cool completely.