This is my mum's recipe and the cornflour seems to give it a lighter texture
4oz plain flour
2oz caster sugar
Sieve the flour and cornflour together. Add the sugar then rub in the butter. The mixture will be very crumbly to start with but continue rubbing in with your fingers until it clings together in heavy lumps. Or alternatively whizz all the ingredients togetgher in a food processor.
Turn onto a board or working surface that has been lightly floured with either cornflour or ordinary plain flour knead the mixture together lightly. Roll into a circle, or press into a shortbread pan/mould or baking tin. Prick all over the top with a fork mark into portions suitable to the pan you are using (you might choose slices, or wedges. If using the circle flute the edge by pinching and moulding the edge.
Bake in a moderate oven for 30 to 35 minutes until the shortbread is cooked but not browned. Leave on baking tray/pan/mould to cool for about 10 to 12 minutes. Then turn out or lift off the circle with a fish slice and place carefully on a wire rack to cool.