In a small saucepan, heat heavy cream until it just begins to boil and remove immediately.
Place chocolate in a bowl and pour hot cream on top.
Let it sit for 1 minute, then stir with a rubber spatula. Stir continuously, until mixture gets smooth. Let it cool to room temperature, before you add it to the mousse cups.
Separate egg yolks and egg whites.
Beat egg yolks with sugar for 5-7 minutes, until pale and frothy. Fold in the Mascarpone cheese, using a rubber spatula. (I do not recommend mixing it in using a mixer).
Beat egg whites until stiff peaks (approximately 3-4 minutes ).
Fold egg whites into the egg yolk Mascarpone mixture.
Add Grand Marnier to the coffee.
Start filling the cups: Add 1 tbsp crushed lady fingers to the bottom of the cups, then add 1 tbsp coffee over the lady fingers. Fill with the cream to about 1/2 full.
Add 1 tbsp crushed lady fingers over the cream and add 1 tbsp coffee over them. Fill cups with more cream leaving 1 centimeter on top, so you can add the ganache.
Add cooled ganache to fill each cup. Chill for 30 minutes. Serve.