For the cake: Preheat the oven to 350 degrees F. Heavily grease and dust with cocoa four 9-inch round cake pans.
In a mixing bowl, combine the flour, sugar and salt.
In a saucepan, melt the butter. Add the cocoa. Stir together. Add the boiling water, allow the mixture to boil for 30 seconds and then turn off the heat. Pour over the flour mixture and stir lightly to cool.
Combine the buttermilk, baking soda, vanilla and beaten eggs. Stir the buttermilk mixture into the butter/chocolate mixture.
Divide the batter among the prepared cake pans and bake for 20 minutes.
Cool completely before icing. Refrigerate the layers after cooling for best results.
For the frosting: Heat the cream until very hot, and then pour over the chocolate pieces. Stir to completely melt, and then pour into the bowl of an electric mixer. Refrigerate to cool.
Once completely cooled, add the vanilla and beat with an electric mixer until light and airy.
Frost the cake in between each layer, on the top and around the sides.