• 250g butter, softened
  • 1 cup pure icing sugar
  • 1 teaspoon vanilla extract
  • 2 1/4 cups plain flour
  • 1/4 cup cornflour
  • 1 eggwhite, lightly beaten
  • 2 tablespoons white sugar
  • Line 2 flat baking trays with baking paper. Draw an 18cm circle in the centre of each sheet of baking paper. Turn paper over so that markings face down.
  • Using an electric mixer, beat butter, icing sugar and vanilla until pale and creamy. Sift flour and cornflour over butter mixture. Stir until a soft dough forms. Turn onto a lightly floured surface. Knead dough until smooth.
  • Divide dough in half. Gently press each piece into a 10cm (diameter) disc. Place shortbread discs on baking trays. Using circles on paper as a guide, gently press shortbread out with your fingers to form a 1.5cm-thick, 18cm (diameter) round.
  • Pinch the edge of each round to form a frill. Score 8 triangles in each shortbread round (do not cut through dough). Refrigerate for 15 minutes or until firm.
  • Preheat oven to 160°C. Brush shortbread with eggwhite and sprinkle with sugar. Bake for 30 to 35 minutes, swapping trays after 15 minutes, or until shortbread is light golden and firm to the touch. Allow to cool completely on trays. To serve, use a sharp knife to cut through markings.