1. Preheat the oven to 180°C, fan 160°C. Line 2 aking trays with baking paper and set aside.
2. Add the flour, orange zest, mixed spice, sugar and butter to a large bowl. Rub together with your fingertips until the mixture resembles fine breadcrumbs. Add the beaten egg and mix until you have a stiff dough. Shape the dough into a disc shape, using your hands, then wrap in clingfilm and allow to chill for 20 minutes.
3. Roll out the dough on a lightly floured surface to 5mm thick. Using a snowflake shaped cookie cutter, cut the dough. Bring any leftover dough together again, roll out and cut out more snowflakes. Transfer to the prepared baking sheets and chill for 10 minutes until firm.
4. Bake for 10-12 minutes (check after 8 minutes if your shapes are small) or until pale golden. Transfer the biscuits to a wire rack and leave to cool completely.
5. To make the icing, put the icing sugar in a bowl, add 3 tbsp water and mix until it forms a thick paste. Put the icing in a piping bag with a small plain nozzle (or spoon into a sandwich bag and snip the corner off to make a small hole). Pipe lines on the cooled biscuits to make a snowflake pattern. Serve and enjoy!