Place the butter and vanilla essence in a mixing bowl and sift in the icing sugar. Cream the ingredients together with a wooden spoon. Sift in the flour and the cornflour a little at a time and fold in with a metal spoon.
Spoon the mixture into a piping bag, and pipe the mixture on to a baking sheet lined with nonstick baking paper, making little flower shapes. To finish a flower, push the nozzle down into the piped flower as you stop squeezing. Press a decoration into the centre of each one.
Bake the cookies in a preheated oven, 190°C (375°F), Gas Mark 5, for 10–15 minutes or until they are a pale golden colour. Remove from the oven and allow to cool for a few minutes on the baking sheet before transferring to a cooling rack.