01 - Melt the chopped dark chocolate in a microwave-safe bowl or over a double boiler until completely smooth. Using a pastry brush or small spoon, coat the insides of 6 silicone or paper cupcake liners with melted chocolate, creating an even layer about 1/8 inch thick. Place the liners on a baking tray and refrigerate for 20 minutes until completely set. Once firm, carefully peel away the liners to reveal the chocolate cups.
02 - Gently melt the remaining dark chocolate in the microwave or double boiler, then allow to cool slightly. In a chilled metal bowl, whip the heavy cream with powdered sugar and vanilla extract using a hand mixer or whisk until soft peaks form. Fold one spoonful of the whipped cream into the melted chocolate to lighten the mixture, then gently fold the chocolate mixture back into the remaining whipped cream until fully combined and smooth.
03 - Pipe or spoon the chocolate mousse into each chocolate cup, filling about two-thirds full. Arrange fresh berries, chopped nuts, mini marshmallows, chocolate curls, and edible gold decorations on top of the mousse in an attractive pattern.
04 - Refrigerate the assembled cups for at least 20 minutes to allow the mousse to set completely. Serve chilled for the best texture and flavor.