Preheat oven to 180ºC conventional or 160ºC fan forced. Place almonds in food processor and process until coarsely ground. Place aside in a bowl.
Cream butter, Caster Sugar and lemon rind in an electric mixer, until light and fluffy. Add egg yolk, flour, nutmeg and ground almonds and mix for a further minute or until mixture forms a dough. (You may need to take mixture out and knead lightly on a floured board to form an even dough). Wrap dough in plastic wrap and store in refrigerator for 20 minutes.
Roll tablespoons of mixture into crescents. Place onto baking paper-lined trays and bake for 15 - 20 minutes or until golden brown. Remove biscuits from oven and dust with Icing Sugar.
Dusting biscuits with Icing Sugar while still warm forms a wonderful sugary coating. The Icing Sugar partly dissolves and coats the biscuits. Store in an airtight container