Sift together the flour and cornflour and set aside. Cream the butter very thoroughly until soft. Add the icing sugar and flavouring and cream in thoroughly. Gradually work in the flour and cornflour until smooth and blended.
Spoon the mixture into a large nylon or cotton piping bag, which has been fitted with a large rosette piping tube. Pipe the mixture into paper baking cases arranged in bun tins or on a baking tray. Pipe twice round the outer edge so there is a hollow in the centre.
Place the cakes in the centre of a moderate oven (180°C., 350°F., Gas Mark 4) and bake for about 20 minutes, or until cooked but still very pale in colour. Cool the cakes thoroughly before dusting each liberally with sifted icing sugar. Finish with a little raspberry jam in the centre of each cake. Makes 12