Preheat Oven to 150°C (300°F).

In a mixing bowl, cream the softened butter and icing sugar until light and fluffy.

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 15 minutes before baking.

Bake for about 15-20 minutes, then turn the oven temperature to 130°C (250°F) for 10 minutes or until lightly golden. They will be crisp and pale.

Let the cookies cool on the baking sheet for a few minutes before transferring to a wire rack. If you want, sprinkle them with caster sugar as soon as they come out of the oven while they are still hot.