Preheat the oven to 180 degrees C. Lightly grease a loose-bottomed 25cm square tin.
Place the plain flour, sugar, butter and ground ginger in a food processor then process until it all comes together in a ball.
Transfer the mixture into the prepared tin then flatten it out with the palm of your hand or the back of a spoon until it is evenly spread. Prick the shortbread all over with a fork. Cut the shortbread into squares or bars now to minimise crumbling after baking.
Bake for 35 minutes or until golden. Remove from the oven and cool for 10 minutes then carefully retrace the cuts with a knife. Cool completely.