This cake is intensely chocolate, rich, moist and an utterly decadent treat.
The cake layers and mousse can be made a day or two ahead. Keep refrigerated until assembly time. Then the whole thing goes into the freezer until serving time. Perfect for entertaining.
If you are fortunate to have a slice or two of cake left, just wrap them and place in your freezer. The frozen slices will keep for up to 3 months.