In a small microwave-safe bowl, combine 1/2 cup of the heavy cream and the chopped sugar-free chocolate.

Heat in 30-second intervals, stirring until the chocolate is fully melted and the mixture is smooth.

Remove the chocolate mixture from heat and allow it to cool to room temperature for approximately 10 minutes.

In a separate large chilled bowl, combine the remaining 1 cup of heavy cream, powdered erythritol, cocoa powder, vanilla extract, and salt.

Using an electric mixer, whip the cream mixture on high speed until stiff peaks form.

Gently fold the cooled chocolate ganache into the whipped cream using a spatula until uniform in color.

Portion the mousse into individual ramekins and refrigerate for at least 2 hours before serving.