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