1. Sieve flour and cocoa twice
2. Cream butter and sugar till light and fluffy
3. Add slightly beaten egg and vanilla essence. Beat well
4. Add flour cocoa mixture gradually beating all the time to a smooth paste
5. Pipe on to a greased and floured baking tray with a large star nozzle into 5cm fingers
6. Bake in a moderate oven for 20 minutes
7. Sandwich two fingers together with butter cream.