Put the butter, sugar, flour and spices in a food processor and pulse until the mixture resembles breadcrumbs. Add the egg yolk and vanilla, and pulse again until it comes together into a dough. Will keep, well wrapped, in the fridge for up to three days, or the freezer for three months.
Roll the dough out on a dusted work surface to the thickness of £1 coin. Use biscuit cutters in the shapes of your choice to stamp out the tags, making sure they’re large enough to pipe names on, about 8-10cm wide (we used round- and star-shaped cutters). Transfer the biscuits, well spaced apart, to baking sheets lined with baking parchment, and chill for 15 mins.
Heat the oven to 180C/160C fan/gas 4. Bake for 12-15 mins until golden at the edges. Leave to cool for 5 mins on the baking sheets, then transfer to a wire rack and leave to cool completely.
Mix the icing sugar with 2-3 tsp water to make a very thick, stiff paste. Colour the icing with food colouring, if you like. Transfer to a piping bag fitted with a very small round nozzle, and pipe borders around the biscuits, then the names in the centre. Leave to set for 2-3 hrs.