Preheat the oven to 190*C/375*F/ gas mark 5. Line a few baking sheets with baking paper or silicon liners.
Cream the butter and sugar together until light and fluffy. Beat in the egg yolks. Sift together the flour, mixed spice and nutmeg. Add the flour mix and milk to the butter cream mixture and mix to make a soft dough. Stir in the currants.
Lightly dust work surface with flour. Roll the dough to a thickness of 1/3" using a floured rolling pin. Cut out rounds using a 3" biscuit cutter.
Utilising the blunt side of a knife, create a gentle cross-shaped indentation on the top of each biscuit. Sprinkle a small amount of Demerara sugar over the biscuits and arrange them on baking trays about 2 inches apart.
Bake for 10 to 15 minutes until puffed and golden brown. Lift onto a wire rack to cool completely.
Store in an airtight container.