Simple and elegant, this is the quintessential French dessert. When you travel to France, no matter the region, you will likely be offered this “chocolate foam” (mousse means “foam” in French). Rich, creamy, dark and dreamy, chocolate mousse is not only a perfect gourmet treat, it also one of the simplest to make.
In a medium bowl, whisk together egg yolks and sugar; set aside. Place 1 C (237 ml) cream in a small, heavy saucepan over medium until bubbles just begin to show around edges. Slowly pour cream into yolk mixture, whisking rapidly until completely combined. Return mixture to saucepan and cook over low, stirring constantly until mixture registers 160°F (71°C) on a candy thermometer. Remove from heat; pour through fine-mesh strainer into large bowl; stir in vanilla.
Place all but garnish chocolate in a microwave-safe bowl; microwave on high for 30-second intervals, stirring between intervals, until chocolate is melted and smooth. Spoon yolk mixture into chocolate; whisk until smooth.
Place remaining cream in a large bowl and beat until stiff; spoon about one cup whipped cream into chocolate mixture, stirring to combine. Add remaining cream, folding in gently just to combine. Spoon or pipe into dessert glasses; garnish with shaved chocolate; chill at least 2 hours or overnight.