1. For the frosting, place the chocolate and cream in a metal bowl and place it over a pot of barely simmering water. Stir the chocolate and cream occasionally and gently until all the chocolate has melted and the mixture is smooth. Remove the bowl from the heat and whisk in the sour cream, vanilla and salt. Let the mixture cool completely to room temperature, stir occasionally (you can chill the mixture for just a few minutes to start it setting, then let it continue to cool naturally at room temperature). Once cooled to a thicker consistency, whisk by hand to thicken just until spreadable consistency (do not whip vigorously or with electric beaters).
2. Place the first cake layers on your serving plate and, if needed, trim the cake to level it. Spread a generous layer of the frosting over the top of the cake. Trim the second cake, if needed and place this on top of the first cake layer. Spread frosting over the top and then the sides of the cake, using swirling motion with your spatula to create a nice design. Chill the cake for at least 2 hours, or until ready to serve.
3. The cake will keep, refrigerated, for up to 3 days.
4. ENJOY YOUR CHOCOLATE CAKE.