Stir together the coffee and grappa or brandy in a bowl. Dip the sponge fingers into the liquid to coat evenly, then arrange half of them in the base of a small shallow dish or serving platter, pouring over any excess liquid.
Whisk together the mascarpone, egg yolks and icing sugar in a bowl until smooth and well blended. In a separate clean bowl, whisk the egg whites until stiff and glossy, then fold the egg whites and the mascarpone mixture together until well blended.
Spoon half the mixture over the soaked sponge fingers and smooth the surface. Scatter half the raspberries over the top. Repeat with another layer of sponge fingers, followed by the rest of the marscarpone mixture and finish with the remaining raspberries on top. Grate the chocolate straight on to the mixture. Cover and chill, preferably overnight, until set.