1.Preheat oven to 150°C. Grease two oven trays.
2.Beat butter and sugar in a small bowl with electric mixer until combined. Add large spoonfuls of sifted flours to butter mixture, beating after each addition. Press ingredients together gently; knead on floured surface until smooth.
3.Divide dough into two portions. Shape portions into 18cm rounds. Place rounds on trays, mark into wedges, then prick with fork. Pinch a decorative edge around the shortbread with floured fingers.
4.Bake about 30 minutes. Stand for 10 minutes before transferring to a wire rack to cool. Cut when cold.