Separate egg, chill egg white. Cream butter and sugar with the whisk of the hand mixer. Stir in the egg yolks first, then the syrup. Mix flour, baking powder, salt and spice and stir in slowly. Wrap the dough in foil and chill for about 1 hour.
Roll out the dough on a floured work surface to a thickness of approx. 4 mm. Cut out cookies with various Christmas motif cutters. Knead the remaining dough and roll out again until the dough is used up. Place the biscuits in portions on 2 baking trays lined with baking paper.
If necessary, prick a hole (with a straw) in the biscuits to hang them up. Bake the biscuits sheet by sheet in a preheated oven (electric cooker: 175 °C/ circulating air: 150 °C/ gas: see manufacturer) for approx. 11 minutes. Take them out, let them cool down on the trays first, then carefully place them on a cake rack and let them cool down.
Stir egg white with icing sugar until smooth. Fill icing sugar icing into a piping bag and cut off a small tip. Decorate cookies with icing and let them dry for about 20 minutes.