Preheat the oven to 180C (350F) and line a cake tin with baking paper.

Cream the butter and sugars together for 2 minutes, or until light and fluffy. Mix in the egg, egg yolk and vanilla and beat to combine.

Add the flour, baking soda and salt to the bowl and beat to combine completely, using a spatula to ensure the flour on the sides is mixed in.

If you’re using cooking chocolate, roughly chop the block into small pieces, and add to the cookie dough. Stir to combine using a wooden spoon.

Press the cookie dough into the cake tin, using your hands to compress it and distribute the dough evenly. If you want you can reserve a bit of dough to make letters to top the cake – I shaped this dough into the letters and placed on a separate baking tray.

Bake in the oven for 22-25 minutes, or until golden brown. Allow the cookie to cool completely before removing from the cake tin, and transfer to a platter.

To decorate, firstly if you have cookie letters, glue these on using an icing of your choice. Then decorate the cake however you want using the icing pens. Top with sprinkles to finish.