Break the chocolate into pieces and process in a food processor until very fine.
Heat the creme fraiche to boiling point and with the processor's motor running, pour it through the feed tube in a steady stream. Process a few seconds until smooth.
Separate the eggs and add the yolks to the hot chocolate mixture. Process for a few seconds to incorporate. Then transfer the mixture to a bowl and allow it to cool until it has thickened to spreading consistency.
In a large mixing bowl, beat the egg whites until stiff peaks form when the beater is raised slowly. Stir about one-fourth of the whites into the chocolate mixture and then carefully fold in the remaining whites until uniform. Pour the mixture into a prepared six-cup souffle dish with a foil collar and freeze for at least three hours. Store up to three days.
When ready to serve, carefully remove the foil collar and serve at once.
YIELD 6 servings
NOTE : To make the foil collar, fasten a band of aluminum foil around the souffle dish with string or paper clips. The band should be four inches higher than the sides of the dish to create the illusion of a risen mousse.