Whisk together the butter and icing sugar. Add in the flour, salt and vanilla and whisk until fully combine.
Once the ingredients form into a dough ball, shape into a rectangular, butter shape, wrap in cling film and place into the fridge for at least 30 minutes.
After at least 30 minutes, slice the dough into 1-inch-thick rectangles with a knife.
Place the cookies on to a baking tray lined with baking paper and place the cookies into the preheated oven for 20 minutes until they are golden brown (rotate the tray after 10 minutes to ensure that they cook evenly).