For chocolate mousse, heat 2 cups cream in a small heavy saucepan over medium heat until it begins to simmer, about 180°. Remove from the heat; whisk in chocolate until smooth. Transfer to a bowl; refrigerate until chilled. Beat until soft peaks form.
For caramel mousse, beat remaining cream in a large bowl until it begins to thicken. Add caramel topping; beat until soft peaks form.
Spoon 3 tablespoons chocolate mousse into six parfait glasses; top with 3 tablespoons caramel mousse. Repeat layers. Refrigerate until serving.