Combine hot water and coffee. Stir in coffee liqueur.
Beat egg whites until peaks just fold over when beater removed.
Beat Tatua Mascarpone, egg yolks, icing sugar and extra coffee liqueur together until thickened. Fold in egg whites.
If using sponge cut to make finger biscuits. Brush coffee mixture over sides of sponge fingers. Arrange a layer of sponge over base of the shallow dish.
Layer with half mascarpone mixture, then remaining sponge. Top with mascarpone mixture, sprinkle over grated chocolate.