Whip butter with an electric mixer until fluffy. Stir in the icing sugar, cornflour, and flour. Beat on low for one minute, then on high for 3 to 4 minutes.
place spoonfulls on cooking paper (on a baking tray) 4 cms apart (or make the shortbread into your desired shapes i.e Christmas Tree's)
Bake for about 9 - 12 minutes. Watch that the edges don't brown too much as this can happen fast. Cool shortbread for about 5 mins before cooling them completely on a wire rack as the shortbread can be quite crumbly when warm.