Break the chocolate into smaller pieces. Place in a heatproof bowl and melt in the microwave 30 seconds at a time, stirring in between until melted. Once melted and smooth, set aside.
In a 4-quart heavy-bottom kettle, whisk together the egg yolks, ¾ cup heavy cream, three tablespoons sugar, and salt. Whisk to combine and set over medium-low heat. Continue to whisk over the heat until the sugar has melted and the mixture registers 160°F. Remove from the heat.
Strain the mousse base through a sieve to remove any lumps or cooked egg.
Stir in vanilla extract and fold the mousse base with the melted chocolate until smooth. Set aside to cool to room temperature.
Using a mixer, whip the remaining 2 cups heavy cream with two tablespoons sugar to stiff peaks, about 3 minutes.
Whisk in about ⅓ of the whipped cream into the chocolate mixture. Once combined, slowly fold in the remaining whipped cream until no streaks of cream are evident.
To serve, spoon or pipe into individual serving dishes. This dessert can also be poured into one large dish.
Place in the refrigerator and chill for at least 6 hours or up to 48 hours. Once chilled, serve with a dollop of whipped cream!