Silky-smooth and cloud-light, this classic chocolate mousse delivers deep, pure chocolate flavor balanced by an airy, velvety texture—elegant yet effortless.
Place the finely chopped chocolate in a medium heatproof bowl.
Heat the heavy cream in a small saucepan over medium heat until it gently simmers (do not boil). Pour over the chocolate and let sit 2–3 minutes, then slowly stir until smooth and fully melted. Set aside to cool slightly.
Combine egg whites, granulated sugar, cream of tartar, and salt in a heatproof bowl set over a saucepan with 2 inches of simmering water (bowl should not touch water).
Whisk constantly until the sugar dissolves and the mixture thins and turns frothy, about 4 minutes, or until it reaches 160°F (71°C).
Transfer to a mixing bowl and whip with a handheld or stand mixer fitted with the whisk attachment on high speed until stiff, glossy peaks form, about 7 minutes.
Gently pour the cooled chocolate ganache into the meringue and fold with a silicone spatula until fully combined and uniform.
Spoon or pipe the mousse into dessert cups, ramekins, or jars.
Refrigerate for at least 4 hours and up to 48 hours; after about 1 hour, cover the mousse.
Garnish with whipped cream, chocolate curls, raspberries, and/or fresh mint before serving.