Add the softened butter and sugar to a food processor. Pulse until well combined and there are no lumps of butter.
First, add the whole egg to the creamed mixture with the food processor running, and pulse until combined. Then add the egg yolk and vanilla and pulse again.
Sift together the flour and salt and add this flour mixture to the egg and butter mixture all at once. Pulse until a dough forms, do not overmix.
Remove the dough from the food processor, cover it in cling film, and refrigerate for an hour.
Preheat the oven to 160°C (320°F) and line two large baking trays with parchment paper.
Remove the chilled dough from the fridge and roll it out on a lightly floured surface to a thickness of ½ cm ( ¼ inch) using a rolling pin.
Use heart-shaped cookie cutters to shape the dough. Place the cookies onto the prepared baking tray in a single layer.
Bake the cookies in a preheated oven for 15 minutes or until the cookies are light golden brown. Allow the baked cookies to cool on a cooling rack.