Place the butter and sugar in a large mixing bowl, then whisk together until pale and fluffy.
Sieve in the flour, then add the vanilla extract. Whisk again until the mixture comes together in a dough.
Roll the dough out on a lightly floured surface to around 1cm thick. Using a small round cookie cutter, cut circles from the dough, then carefully transfer them to the baking trays.
Bake for around 15 minutes until golden.
Once cooked, leave the shortbread rounds to cool on the baking trays for a few minutes then transfer to a cooling rack to finish cooling.
Divide the fondant icing in two. Keep half white, then split the other half into 3 or 4 pieces and colour them with bright gel food colourings.
Roll the white fondant out and cut fluted circles using a similar sized cookie cutter to the one you used to cut out the cookies. Place a white fondant circle on the top of each cookie.
Roll out the coloured icings and cut numbers from them using mini number shaped cutters. Pop a number on top of each cookie – sticking it in place with a splash of water if needed.
Store the cookies in an airtight container, layered with baking paper to separate them, until ready to serve.
