Dark chocolate was melted with the liquid, a water bath or in a microwave oven. Melted chocolate mixed with crushed biscuits and the resulting dough is affixes the bottom of a baking dish or pan. The prepared pan is left to cool to set. Meanwhile, prepare chocolate mousse. Water bath melt the butter, chocolate and milk. In a separate bowl, beat egg yolks with sugar and there is added while stirring the chocolate mixture. Separately, mix the cream and add to the chocolate mixture carefully - without intense agitation, but rather to roll. Musat pour over the biscuit base and leave to cool for at least four hours. Top decorated with melted white or milk chocolate, crushed nuts and other optional.