Line a large baking tray with baking parchment.
Put the butter and sugar in a bowl and whisk together well until smooth and creamy.
Whisk in the egg yolk and Vanilla Extract.
Sift the flour and spice on top and add the currants.
Mix all the ingredients together until well combined, and then bring the mixture together with your hands to make a fairly soft dough.
Turn onto a lightly floured surface and knead gently until smooth.
Roll out thinly to a thickness no greater than ½ cm (1/4 inch). Using a 6cm (2 ½ inch) crinkle edged round cutter, stamp out 12 rounds, re-rolling as necessary and place on the baking trays, spaced a little apart. Prick with a fork.
Chill for 30 minutes.
Preheat the oven to 200˚C (180˚C fan assisted oven, 400˚F, gas mark 6).
Bake the biscuits for about 12 minutes until lightly golden round the edges.
Leave on the tray for 5 minutes then transfer to a wire rack to cool completely.