01 - Melt the chocolate in a heatproof bowl over simmering water, stirring until smooth. Remove from heat and let cool slightly.
02 - Beat the egg yolks with 2 tbsp sugar and vanilla extract until thick and pale.
03 - Stir the cooled chocolate into the yolk mixture until well combined.
04 - Beat the egg whites with salt until foamy. Gradually add remaining 2 tbsp sugar and beat until stiff peaks form.
05 - Whip 3/4 cup heavy cream until soft peaks form.
06 - Gently fold the whipped cream into the chocolate-yolk mixture.
07 - Carefully fold in the beaten egg whites in two additions, ensuring the mixture stays light and airy.
08 - Spoon the mousse into individual serving glasses or bowls. Cover and chill for at least 2 hours until set.
09 - Whip 2/3 cup heavy cream with powdered sugar and vanilla extract until soft peaks form.
10 - Pipe or spoon the whipped cream over the chilled chocolate mousse just before serving.