Heat the cream over medium heat until it begins to simmer, then pour over chopped dark chocolate. Let it sit for a minute, then stir until smooth and glossy. Add butter if desired for shine. Spoon into six small glasses, filling one-quarter full, and chill.

For the pistachio paste, blend pistachios, sugar, salt, and vanilla in a food processor until smooth. Add a little cream if needed for texture. For a brighter green, blanch and peel the pistachios before blending.

Whip cold heavy cream to soft peaks. In another bowl, beat mascarpone and fold in pistachio paste, then gently mix in whipped cream until light and fluffy.

Once the ganache is set, spoon or pipe the pistachio mousse on top. Smooth the surface, cover, and refrigerate for at least two hours until firm.

Before serving, top each glass with chopped pistachios, chocolate curls, and a touch of gold dust or sea salt flakes. Serve chilled.