Whisk together icing sugar and egg until well combined.
Add lemon rind and vanilla essence.
Add the ground almonds and mix well.
On a surface dusted with icing sugar, knead the mixture together.
Shape the mixture into balls and place on a baking tray, and press with a fork or cookie stamp to flatten, then dust with a little icing sugar.
Bake at 170c for approx. 15mins.