Preheat the oven to 180C/160C Fan/Gas 4. Line a baking tray with greaseproof paper.
Cream the butter and sugar together in a bowl until pale, light and fluffy. Crack in the egg and add the vanilla extract, then beat again.
Mix in the flour, cinnamon and candied peel until the mixture comes together as a dough.
Roll the dough out on a lightly floured work surface to a thickness of 1cm/½in.
Using biscuit cutters or a glass, cut biscuits out of the dough and carefully place onto the baking tray. Decorate with the almond halves. To make into Christmas tree decorations, carefully make a hole in the top of the biscuit using a straw.
Bake the biscuits for 8-10 minutes until deep golden-brown. Set aside to harden for 5 minutes, then cool on a wire rack.