ip half the sponge fingers in the mixed coffee and cognac, and put in the bottom of a glass bowl. Blend mascarpone, yoghurt, ricotta, sugar and vanilla extract until smooth. Whip the egg whites until stiff and fold into mixture. Spoon half of the mixture in the bowl. Cover with the remaining sponge fingers, dipped in the coffee and cognac mixture and spoon on the rest of the cream. Sprinkle the surface with chocolate and ground coffee, cover and refrigerate for several hours before serving.