Heat oven to 200C/180C fan/gas 6 and line a baking sheet with baking parchment. Put the butter in a bowl and beat it with electric beaters until soft and creamy. Beat in the sugar, then the egg and vanilla, and finally the flour to make a dough. If the dough feels sticky, add a little flour and knead it in. Chill for 20 mins in the fridge.
Roll the dough to about the thickness of a £1 coin on a lightly floured surface. Cut out snowflake shapes using a biscuit cutter, then re-roll the off-cuts and repeat.
Bake for 8-10 mins or until the edges are just beginning to brown. Leave to cool for 5 mins before trying to move them. Cool completely.
Roll out the fondant icing to the thickness of a 50p piece. Use the same cutter to stamp out the icing. If you have smaller cutter you can stamp out holes in the middles of some of them. Brush each biscuit with a tiny amount of honey and press an icing snowflake on top.
Mix the icing sugar with enough water to make a pipeable icing, and spoon it into a piping bag fitted with a straight piping nozzle. Pipe patterns onto the snowflakes and add silver balls and sprinkles as you decorate. Leave to dry completely.