Beat the butter, jam, sugar, egg and salt in a bowl until the mixture becomes lighter in colour. Add the flour, mix to create a soft dough, do not knead, cover and refrigerate for approx. 1 hr.
On a lightly floured surface, roll out the dough in batches to approx. 4 mm thick. Cut out 38 rabbits (approx. 7 cm. long) using a rabbit cutter, place on two trays lined with baking paper.
Approx. 15 mins. in the centre of an oven preheated to 160 °C (convection). Remove from the oven, allow to cool a little, then leave to cool completely on a rack.
Combine the jam with the lemon zest, spread over half of the biscuits, place the remaining biscuits on top.
Dip the rabbits' ears in the cake icing, leave the biscuits to dry on a sheet of baking paper.