Preheat the oven to 200oC/400oF/Gas
6. Lightly grease two baking sheets. Cream together the butter or
margarine and sugar until light and fluffy, then beat in the egg yolk.
Sift the flour and spices over the egg
mixture, then fold in with the currants and peel, adding sufficient milk
to make a fairly soft dough.
Turn the dough on to a floured
surface, knead lightly until just smooth, then roll out using a floured
rolling pin, to about a 5mm thickness.
Cut the dough into circles to the
baking sheets and bake for 10 minutes.
Beat the egg white, then brush over
the biscuits.
Sprinkle with caster sugar and return
to the oven for a further 10 minutes, until golden.