method
1. Sift the flour and cornstarch together. Cream the butter until soft, then add the superfine sugar and beat until the mixture is pale and creamy.
2. Gradually work the orange rind and flours into the mixture.
3. Lift the shortbread on to a large baking tray. Roll it out to give a 8 inch circle.
4. Pinch the edges and prick the shortbread with a fork. Cut into sections with the blunt edge of a knife, then sprinkle with a little superfine sugar.
5. Chill for 15 minutes, then bake in a moderate oven (160°C, 325°F) for 35 minutes or until pale golden.
6. Cool on the baking tray for a few minutes, then transfer to a wire rack to cool.
