Method

• 1.
  Line 2 trays with baking paper.
• 2.
  Using electric beaters, beat butter and sugar in a bowl until just pale and creamy. Beat in egg, mixing well, then the zest. Fold in flour and cocoa to combine, then tip onto a lightly floured surface and knead briefly to form a smooth dough. Enclose in plastic wrap and chill for at least 1 hour.
• 3.
  Halve dough. On a floured surface, roll out each piece to about 5mm thick. Using a decorative cutter (we used bat and cat cutters), cut out shapes and place on trays, leaving a 2-3cm gap between biscuits. Chill for a further 30 minutes on the trays.
• 4.
  Preheat oven to 180°C. Bake biscuits for 10 minutes until dry. Transfer to a rack to cool before decorating with icing.