Blend the biscuits and nuts in a blender or food processor. Then add the soft butter and mix well. Lay out a baking dish with removable bottom with baking paper. Spread out the crumbs of biscuits and nuts, press with your fingers well.
To prepare the cream, heat the liquid cream well, remove it from the heat and add in the chocolate. Stir well, until you get a smooth cream. Pour the cream over the biscuit layer and set aside a small portion for the upper layer. Arrange a line of whole biscuits. Put the form in the fridge to set.
Meanwhile, make the mocha cream, by melting the chocolate and butter in a water bath over low heat. Remove from the heat as soon as they become homogenized and beat the yolks in. Add the coffee, 1/3 of the cream and gelatin, swollen and dissolved in a water bath in a little water. Beat well and leave thus prepared mocha cream to cool.
Beat the remaining cream to hard snow with the sugar and add it to the cooled cream. Pour the mocha cream on the biscuits and arrange another layer of biscuits.
Spread on the allocated cream from the first layer. Then pour on couverture chocolate over the cake and make decorations of your choice. Put in the refrigerator for several hours.
Before serving, remove the sides of the form and baking paper.