Preheat the oven to 180°C/160°C fan/Gas Mark 4.

Grease the Le Creuset Insulated Cookie Sheet with a little butter. For the biscuits, beat the butter with the icing sugar until smooth, then beat in the raspberry extract if using. Next, sift over the flour and cornflour and beat in until smooth and very stiff.

Spoon half of the mixture into a piping bag fitted with a 12mm star nozzle. Pipe 5cm wide rosettes, 5cm apart on the cookie sheet and bake for 10-12 minutes until they are richly golden around the edges, but the centres will remain pale. Leave to cool on the tray, then slide onto a cooling rack, taking care as they are very delicate.

For the filling, beat the butter, icing sugar and vanilla extract until smooth. Spread the underside of one biscuit with a thin layer of buttercream and another biscuit with jam. Sandwich together, then dust with a little icing sugar and raspberry powder.

Cook's Notes

The freeze-dried raspberry powder is available from specialist baking suppliers and online. Alternatively, freeze-dried raspberries are available in the baking aisle of most major supermarkets, and can be ground with a mortar and pestle to give a finer powder.

To help guide you when piping out the biscuits, dust the greased cookie sheet lightly with flour, then knock off the excess. Gently mark with 5cm circles using a plain pastry cutter.

The flavour of the Viennese Whirls can be varied for delicious alternatives. Simply omit the raspberry flavouring, jam and powder. Instead, use strawberry essence and strawberry jam and dust with icing sugar and strawberry powder. Use vanilla extract in the biscuits and blueberry jam in the filling, dusting them with icing sugar and blueberry powder. You can also add orange, lemon or lime zest to the biscuit mixture and fill it with fruit curd and whipped cream.