01 - Melt chopped dark chocolate in microwave-safe bowl or over double boiler until smooth. Using pastry brush or spoon, coat insides of 6 silicone or paper cupcake liners with melted chocolate, creating even layer. Place liners on tray and chill in refrigerator for 20 minutes or until set. Once firm, carefully peel off liners, leaving chocolate cups.
02 - Gently melt dark chocolate in microwave or double boiler and let cool slightly. In chilled bowl, whip heavy cream with powdered sugar and vanilla extract until soft peaks form. Fold spoonful of whipped cream into melted chocolate to lighten, then gently fold chocolate mixture into remaining whipped cream until fully combined and smooth.
03 - Pipe or spoon chocolate mousse into each chocolate cup, filling about two-thirds full. Garnish with fresh berries, chopped nuts, mini marshmallows, chocolate curls, and edible gold decorations as desired.
04 - Chill assembled cups in refrigerator for at least 20 minutes before serving.