Melt chocolate in double boiler
Whip the egg whites until frothy and then add the salt. Continue whipping until soft peaks form.
Gradually add the sugar, one tablespoon at a time, and beat on high speed until stiff, glossy peaks form.
Stir a small amount of the whipped egg whites into the melted chocolate to lighten it.
Gently fold the remaining egg whites into the chocolate mixture in batches. Use a spatula and fold carefully to avoid deflating the mixture.
Spoon into serving dishes and refrigerate for at least 2-3 hours, or until set.