Melt the Chocolate:

• In a heatproof bowl, melt the dark chocolate over a pot of simmering water (double boiler method), stirring until smooth.
• Remove from heat and let cool slightly.

Prepare the Egg Yolk Mixture:

• In a mixing bowl, whisk the egg yolks with half of the sugar until pale and slightly thickened.
• Stir in the melted chocolate and vanilla extract until well combined.

Whip the Egg Whites:

• In a separate bowl, beat the egg whites with a pinch of salt until soft peaks form.
• Gradually add the remaining sugar and continue beating until stiff peaks form.

Whip the Heavy Cream:

• In another bowl, whip the heavy whipping cream until soft peaks form.

Assemble the Mousse:

• Gently fold the whipped cream into the chocolate mixture.
• Then, carefully fold in the beaten egg whites, maintaining the light and airy texture.

Chill and Serve:

• Divide the mousse into serving glasses and refrigerate for at least 2 hours, or until set.
• Garnish with whipped cream and chocolate shavings before serving.