Preheat oven to 150 C. Line 2 biscuit trays with baking paper.
In a bowl of a stand mixer, add butter and icing sugar. Cream butter and icing sugar until light and creamy. Add orange zest. Mix in cornflour and flour. Mix till you form a dough.
Tip out the dough onto a lightly floured surface and shape it into a disc. Cover in glad wrap and refrigerate for 30 minutes.
Take the dough out of the fridge and roll out to 1 cm thickness. Cut into fingers. Prick with a fork. Bake 25-30 minutes, until pale but crisp.