Perfect shortbread biscuits with a hint of vanilla. You can find vanilla sugar in larger supermarkets or you can make your own by placing a vanilla bean in a airtight container filled with caster sugar; let it sit for a week and you'll have your very own vanilla sugar to use in these shortbread biscuits!
For extra vanilla flavour, replace all or some of the caster sugar with vanilla sugar. If you don't have vanilla sugar, you could also use about 1/2 teaspoon vanilla extract.