In large bowl, combine chopped chocolate, marshmallows and 1/2 cup heavy cream. Microwave 2 minutes on high, or until marshmallows are melted. Let mixture cool 1 hour.

Using mixer, whip 1 3/4 cups heavy cream until soft peaks form. Reserve and refrigerate 1/2 cup whipped cream for topping.

In cooled chocolate mixture, fold in 2 cups whipped cream until combined. Add remaining whipped cream and mix until combined.

Spoon mousse into ramekins. Refrigerate at least 2 hours.

To serve, top with 1/2 cup reserved whipped cream and sprinkle with shaved chocolate, if desired.