In a medium mixing bowl, combine the egg yolks and granulated sugar. Whip for about 2 minutes until pale and fluffy.

In a saucepan, gently heat 3/4 cup of heavy cream with a pinch of sea salt over low heat for 3-5 minutes.

While whisking, slowly pour the warm cream into the egg yolks to temper. Then, return the mixture to the saucepan.

Whisk constantly over low heat until thickened and reaches 160°F, about 3-5 minutes.

Remove from heat and stir in chopped bittersweet chocolate and vanilla extract until melted and smooth.

Pour the mixture into a bowl, cover with plastic wrap, and chill in the refrigerator for 30-40 minutes.

Whip remaining heavy cream in a chilled bowl until stiff peaks form.

Gently fold the whipped cream into the cooled chocolate mixture until just combined.

Transfer the mousse into serving cups, chill for at least 2 hours before serving.