Combine the cream, mascarpone, Marsala and sugar in a large mixing bowl and whisk until the mixture has the consistency of thickly whipped cream. Pour the made up coffee into the a shallow dish.
Dip the sponge fingers into the coffee, turning for a few seconds so that they are evenly soaked, then layer half into the base of a 2 pint souffle dish. Spread half of the mascarpone mixture on top of the sponge fingers, then layer the other half of sponge fingers on top.
Sprinkle the grated chocolate on top, then spoon the remaining mascarpone mixture on top and smooth with a palette knife so that it is flush with the rim of the dish. Sift the cocoa powder on top in an even layer and serve.