Preheat the oven to 180 C/ 350 F
In a food processor mix the butter, sugar, and vanilla until smooth
Add the flour, egg, and egg yolk and process until the mixture forms a soft dough
Take the dough out of the processor and knead slightly bringing it together in a ball. Wrap it in cling film and place it in the fridge for 30 minutes
Roll the dough out between 2 sheets of baking paper or on a lightly floured surface until about ½ cm / 5mm thick
Cut the dough into shapes approximately 7cm (or as desired). Ensure the sizes are similar when baking in each batch.
Place the dough rounds on a baking sheet that has been lined with baking paper or silicone baking sheets
Bake for 10 – 12 minutes until golden brown (check at 10 minutes). Rotate the pan halfway through the cooking time to ensure an even baking and if necessary.
Remove the biscuits carefully from the baking tray and allow them to cool on a wire cooling rack as they have a tendency to carry over cooking on the tray and could turn too brown once removed from the oven.
When cooled, dust them with some icing sugar or decorate them as desired.