Pistachio Lime Balls

250g butter, softened
Rind of 2 large limes, finely grated
1/2 cup pure icing sugar
2 cups plain flour, sifted
1 cup roasted pistachio nuts, coarsely ground
Green sugar
Icing sugar, extra

Beat butter and lime rind in large bowl until pale. Add icing sugar and beat. Add flour and beat until combined. Add nuts and use a wooden spoon t o mix until dough comes together. Preheat oven 180C. Line oven trays. Roll dough into small balls, then roll in green sugar to coat. Put balls on trays and flatten slightly. Refrigerate until form, approx 15mins. Bake 1 tray at a time for 12-15mins or until bases are light golden. While biscuits are hot, sprinkle with extra icing sugar. Stand 10mins on trays then transfer to wire rack to cool.