1.Beat butter, caster sugar, dusting sugar and vanilla in a large bowl with an electric mixer until pale and fluffy. Stir in the sifted flours; press mixture together to form a firm dough. Knead gently on a lightly floured surface until smooth. Divide in half, cover, refrigerate for 30 minutes.
2.Preheat the oven to slow (150°C/130°C fan- forced). Lightly grease oven trays.
3.Roll half the dough between two sheets of baking paper until 1cm thick. Using a 6cm fluted cutter, cut rounds from the dough; from each round, cut a hole in the centre with a 1.5cm fluted cutter. Re-roll scraps and repeat.
4.Place rounds on greased oven trays, sprinkle with the white sugar. Repeat with the remaining dough.
5.Bake shortbread for about 30 minutes or until a pale straw colour. Stand the shortbread on the trays for 5 minutes; transfer to a wire rack to cool.
To give as a gift, thread ribbon through the centre of the shortbread and tie into a ring. Or, you can hang shortbread from the Christmas tree.Note