Using your hands, knead the dough lightly and form into two flat discs. Wrap in cling film and place in the refrigerator to chill for 30 minutes.
Lightly dust your work surface with some beremeal flour and roll out the dough (it will still be fairly soft) to a four mm thickness.
Cut with a round cutter and place on your prepared baking tray and using the tines of a fork poke a few holes in the top of each biscuit.
Bake for 12-15 minutes until lightly golden. Dust with extra caster sugar as soon as they come out of the oven and leave to cool a few minutes on the baking tray before transferring to a wire rack to cool completely.