Dark and white chocolate mousses on a coffee sauce

Also known as the odd couple, this pair of mousses are opposites in many ways, though almost Identical in their content. One is dark, heavy, intense; the other white, airily light and delicate. The only thing holding together the texture of the mousse is whipped cream, no gelatines nor other support systems, and almost the only flavour is chocolate, as much as the cream can possibly hold up. It hardly needs to be said that the best chocolate you can get your hands on is vital in these circu