Cream butter with castor sugar until light and fluffy. Add egg yolk and beat well. Stir in flour alternately with nuts. Knead mixture lightly and form into a ball. Roll small pieces of dough into balls the size of large hazelnuts. Roll under the palm of the hand to form a small tube and then shape into crescents. Place on greased baking trays and bake in a preheated slow oven 150C (300F) for 12-15 minutes. While still warm, toss biscuits in icing sugar and place on wire racks to cool. Serve in tiny paper patty cases, if you wish. Makes 70.
GREEK SHORTBREADS: Roll dough in balls, push a whole clove in each one and bake as above.