Separate your eggs, whisk the yolks with the sugar until pale and fluffy, and fold in the mascarpone until mostly combined and moussey.
Whip your egg whites until soft peaks, and fold into your mascarpone mixture.
Put the coffee in a shallow dish, large enough to fit a biscuit in.
Dip each biscuit one at a time, for 3 seconds (completely submerged) and place at the bottom of your serving dish. Don't worry if your biscuit still feels "crunchy" in the middle, it will soften on standing. Be careful not to oversoak, or they will fall apart.
Top with a layer of the mascarpone mousse, and repeat with another layer of coffee-soaked biscuits.
Once you have used all your biscuits and mousse, grate your chocolate and sprinkle over the top, until mousse is completely covered.
Refrigerate overnight (ideally).
Reprinted with permission of The Gorgeous Gourmet
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