Preheat Oven to 150°C (300°F).
Cream the Butter and Sugar. In a mixing bowl, cream the softened butter and icing sugar until light and fluffy.
Sift in Dry Ingredients. Sift in the cornflour and flour, mixing until just combined to form a dough.
On a lightly floured surface, press the dough into a rectangular log about 20cm long x 6cm wide x 4cm high. Cut into 1cm thick slabs and slice these in half lengthwise to make 2cm x 6cm rectangles (to get roughly 30 cookies). Prick each cookie 3 times with a fork.
Place on a lined baking sheet and chill in the fridge for 10 minutes.
Bake for about 15-20 minutes then turn down the oven temperature to 130C (250F) for 10 minutes or until lightly golden. They will be crisp and pale. (Optional: Sprinkle with sugar when hot out of the oven).
Cool. Let the shortbread cookies cool on the baking sheet for a few minutes before transferring to a wire rack.
