Melt the chocolate in a water bath and let it cool down a little. Whip the mascarpone loosely. Beat the cream with the sugar until stiff. Mix the melted chocolate with mascarpone and fold in the cream. Let the cream rest until it hardens a little.
In the meantime, crumble the biscuits and cut the pralines into small pieces. Add the nuts, coffee and liqueur and mix everything carefully. Put a thin layer of nuts in a glass bowl. Put a layer of mascarpone cream on top. Repeat this process two more times. Let the dessert soak in the refrigerator overnight or for a few hours.