100g unsalted butter, softened at room temperature
100g caster sugar
1 medium free-range egg, lightly beaten
275g plain flour
1 tsp vanilla extract
400g icing sugar
3-4 tbsp water
2-3 drops food colourings
Preheat the oven to 190C/170C Fan/Gas 5. Line a baking tray with greaseproof paper. Cream the butter and sugar together in a bowl until combined. Beat in the egg and vanilla extract, a little at a time, until well combined. Stir in the flour 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, cut biscuits out of the dough and carefully place onto the baking tray. Bake for 8-10 minutes, or until pale golden-brown. Set aside to harden for 5 minutes, then cool on a wire rack. For the icing, sift the icing sugar into a large mixing bowl and stir in enough water to create a smooth mixture. Stir in the food colouring. Carefully spread the icing onto the biscuits using a knife and set aside until the icing hardens.