01 - Melt the dark chocolate in a heatproof bowl over simmering water, stirring constantly until smooth. Remove from heat and allow to cool slightly.
02 - Whisk egg yolks with half the granulated sugar and vanilla extract until the mixture becomes pale and thick.
03 - Gradually incorporate the melted chocolate into the egg yolk mixture, stirring continuously until fully combined.
04 - In a clean bowl, whip egg whites with a pinch of salt until soft peaks form. Slowly add the remaining sugar and continue whipping until stiff peaks develop.
05 - Carefully fold the whipped egg whites into the chocolate mixture in three additions, preserving as much air as possible.
06 - Whip the measured heavy cream until soft peaks form, then gently fold into the chocolate mixture until smooth and homogenous.
07 - Distribute the mousse evenly into four serving glasses or ramekins. Cover and refrigerate for at least two hours to set.
08 - Beat the chilled heavy cream with powdered sugar and vanilla extract until soft peaks form, creating a light and airy topping.
09 - Top each set mousse with a generous dollop of the whipped cream immediately before serving.