Mix the water with 9 oz (250 g) of the chocolate and melt it it slowly in a water bath. Dissolve the gelatin in 2/5 cup (100 ml) water and after 20-30 min. pour in 1 cup of hot water into it. Let it cool and add the cognac to it.
Beat the cream with the remaining sugar but set aside a little for decoration. Mix the chocolate cream, gelatin and sweet cream and flavor with vanilla.
Pour the chocolate mousse into cups and let them sit for 1 hour in the fridge. Decorate the jellied mousse with cream and a little grated chocolate.