01 - Melt dark chocolate in a heatproof bowl set over simmering water or in short bursts in the microwave. Using a pastry brush or spoon, generously coat silicone dome molds (7–8 cm diameter) with melted chocolate. Chill for 10 minutes to set, then repeat the process to thicken the shell. Refrigerate until shells are fully set, about 30 minutes.
02 - Soften gelatin leaves in cold water for 5 minutes, or bloom powdered gelatin in 2 tablespoons cold water. In a mixing bowl, whisk mascarpone cheese with powdered sugar and vanilla until combined. Whip the cold cream to soft peaks, then gently fold into the mascarpone base. Gently heat gelatin until fully dissolved and incorporate into the mousse. Spoon or pipe mousse into chocolate shells, filling almost to the top, then smooth the surface. Chill for at least 3 hours until fully set.
03 - Carefully unmold the set domes from the silicone molds and place each dome on a wire rack over a tray to prepare for glazing.
04 - Soften gelatin in 3 tablespoons cold water. In a saucepan, combine water, granulated sugar, heavy cream, and sifted cocoa powder. Simmer gently, whisking until the mixture is uniform and smooth. Remove from heat, let cool slightly to 122°F, then whisk in softened gelatin until fully dissolved. Allow glaze to cool further to 90°F for ideal pouring viscosity.
05 - Pour the mirror glaze evenly over each dome, ensuring full coverage as excess drips away. Transfer domes onto dessert plates. Adorn with gold leaf, chocolate curls, or fresh berries if desired. Refrigerate for at least 30 minutes to set the glaze before serving.