Place the softened butter, caster sugar and vanilla extract into the bowl of an electric mixer and mix on a medium - high speed for 4 minutes, or until the mixture is pale and creamy.
Add the flour, egg and extra egg yolk and beat on a low speed until a dough begins to form.
Transfer the dough to a lightly floured bench and use your hands to bring it together (don’t worry, it will be crumbly) and lightly knead into a smooth ball. Cover in cling wrap and pop into the fridge for 30 minutes to chill.
Preheat your oven to 180 degrees celsius. Roll out dough (thickness of 5mm) between two sheets of baking paper and using your choice of a cookie cutter, cut out shapes and place onto your prepared trays.
Bake in oven for 10-12 minutes or until the biscuits begin to turn golden around the edges. Leave the biscuits to cool on the trays for 10 minutes before carefully transferring to a wire rack to cool completely
Please note your cooking time will vary depending on the size of the biscuit cutter that you use.You can make this dough a couple of days in advance and store in the fridge until neede