Preheat oven to 180 C / 160 C fan and line a baking tray with a silicone baking mat or baking paper.
Cream the butter and sugar together until light and fluffy. I use my Optimum ThermoCook and select CHOP for 60 seconds.
Add the remaining ingredients and combine thoroughly. If using the ThermoCook select CHOP for a further 60 seconds.
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.
Mum of three, daydream adventurer, OU Life Sciences graduate, occasional crafter, ex-pat Canadian & quite possibly Britain's most northerly food blogger.