01 - Gently melt chopped dark chocolate in a heatproof bowl set over simmering water, or microwave in 20-second bursts until smooth. Using a pastry brush or spoon, coat silicone dome molds (approximately 3-inch diameter) with a thick layer of melted chocolate. Refrigerate for 10 minutes to set. Apply a second layer for extra durability and return to the refrigerator for at least 30 minutes, until shells are fully firm.
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, powdered sugar, and vanilla until smooth.
03 - Whip heavy cream to soft peaks using an electric mixer or whisk. Gently fold the whipped cream into the mascarpone mixture until smooth and even.
04 - Warm softened gelatin until dissolved but not hot, then fold gently into the mousse mixture. Spoon or pipe the mousse into prepared chocolate shells, filling nearly to the top and smoothing the surface. Chill molds for at least 3 hours, allowing mousse to fully set.
05 - Carefully release domes from silicone molds. Set on a wire rack over a tray, preparing for glazing.
06 - Soften gelatin in 3 tablespoons cold water. In a small saucepan, combine water, sugar, heavy cream, and sifted cocoa powder. Bring to a simmer over medium heat, whisking constantly until smooth. Remove from heat and cool slightly to about 122°F (50°C), then stir in gelatin until fully dissolved. Allow glaze to cool further to 90°F (32°C) for optimal pouring consistency.
07 - Pour smooth chocolate glaze over each dome, ensuring a complete and glossy coating as excess drips off. Transfer domes to serving plates. Adorn with gold leaf, chocolate curls, or fresh berries as desired. Refrigerate domes for at least 30 minutes to set the glaze before serving.