01 - Melt 7 oz dark chocolate in a heatproof bowl over simmering water. Use a pastry brush to coat the insides of 4 silicone muffin molds or paper cupcake liners with melted chocolate. Chill for 10 minutes, then apply a second coat. Chill until fully set, about 30 minutes.
02 - Carefully peel away molds or liners to release the chocolate cups. Store in the refrigerator until ready to fill.
03 - Melt 5.3 oz dark chocolate in a heatproof bowl over simmering water. Allow to cool slightly.
04 - In a bowl, beat egg yolks with 1 tbsp granulated sugar until pale and creamy. Stir in the cooled chocolate and vanilla extract.
05 - In a separate clean bowl, whisk egg whites with a pinch of salt until soft peaks form. Gradually add 1 tbsp sugar and continue whisking until glossy.
06 - In another bowl, whip 5 fl oz heavy cream until soft peaks form.
07 - Gently fold whipped cream into the chocolate mixture, then fold in the egg whites in two additions until just combined.
08 - Spoon the mousse into prepared chocolate cups. Refrigerate for at least 1 hour to set.
09 - Whip 3.4 fl oz chilled heavy cream with powdered sugar until soft peaks form. Pipe or spoon over set mousse.
10 - Garnish with chocolate shavings or a dusting of cocoa powder. Serve chilled.