Melt chocolate in a double boiler or a metal bowl set over a pan of simmering water, stirring frequently, then cool.
Beat whipped cream in a planetary mixer until it just holds stiff peaks. Whisk one fourth of cream into chocolate, and then fold in remaining cream gently but thoroughly while adding the hazelnut paste.
Spoon mousse into pyramid shape Silicon moulds and chill.
To plate de-mould the mousse pyramid place on a plate with chocolate soil, chocolate sponge, and hazelnut candy.