Break cake into 2i nch pieces onto a cookie sheet. Sprinkle with rum.Set aside. Melt chocolate over simmering water in double boiler, stirring constantly. Add eggs, 1 at a time. Add vanilla and salt and cook,stirring for a minute. Remove from heat and cool slightly. Whip 1/2 pint of the whipping cream, adding 2 Tbsp. sugar gradually til stiff peaks form. Fold into chocolate mixture.
In a buttered 9 inch springform pan, layer cake with chocolate mixture, beginning and ending with cake. There should be 3 layer of cake and 2 of chocolate. Refrigerate cake for at least 6 hours
After that time, run a sharp knife around sides of pan and then remove pan sides. Whip remaining pint of whipping cream with 3 Tbsp. powdered sugar and generously frost top and sides of cake. Sprinkle with chopped nuts or shaved chocolate. Store in refrigerator or cover and freeze. Serves 10 to 12