Preheat oven to 180 degrees Celcius.
Cream margarine and icing sugar until light and fluffy.
Sift cornflour and flour into the sugar and margarine and mix until just combined.
Roll out half the mixture at a time on a floured board until just less than 1cm thick.
Cut shapes and put onto an oven tray.
Re-roll leftover until you have used all the dough.
Do the same with the other half.
Bake for around 10 minutes – careful not to burn the edges.
Cool on over tray then transfer onto a wire rack.
Optional: Ice once your shortbread has cooled completely.