1. Melt the chocolate:

• In a heatproof bowl, melt the chopped dark chocolate over a double boiler or in the microwave (in 20-second intervals, stirring until smooth). Allow it to cool slightly.

2. Whip the egg whites:

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

3. Whip the cream:

• In another bowl, whip the heavy cream with the remaining sugar and vanilla extract until soft peaks form.

4. Combine the mixtures:

• Stir the egg yolks into the slightly cooled melted chocolate until well combined. Then gently fold in the whipped egg whites in three parts, being careful not to deflate the mixture. Finally, fold in the whipped cream until fully incorporated.

5. Chill:

• Spoon the mousse into individual serving dishes or a large bowl. Refrigerate for at least 1 hour (or up to 2 hours) to allow it to set.

6. Serve:

• Once chilled, serve the mousse as is or with toppings like whipped cream, chocolate shavings, or fresh berries.