Heat the oven 170C/150C fan/gas 3. Put the flour, butter and sugar into a mixing bowl.

Use your hands to combine the ingredients until the mixture looks like breadcrumbs, then squeeze until it comes together as a dough.

On a lightly floured surface, use a rolling pin to roll out the dough to 1/2 cm thick.

Cut the dough into fingers and place on a lined baking tray. Use a fork to create imprints.

Then sprinkle with the remaining caster sugar.

Chill the dough in the fridge for 20 mins, then bake for 15-20 mins until golden brown. Remove the shortbread fingers from the oven and leave to cool on the tray for 10 mins.