Place the chocolate in the top of a double boiler filled with simmering water. Let the chocolate melt, stirring occasionally.
Alternatively, you can melt the chocolate in a glass bowl in the microwave, cooking in 30-second increments, stirring in between.
Allow the chocolate to cool slightly.
In the bowl of a stand mixer, beat the egg whites to soft peaks.
In a medium bowl, whip the heavy cream with the Swerve and vanilla until it is well combined.
Add the creme to the chocolate, and stir until it is thoroughly combined.
Add the egg whites gently.
Divide the mousse between serving dishes and refrigerate for at least 1 hour.