This is a recipe from Gourmet which I have changed to be even more seductive. It is an incredible cake! There are no shortcuts with this cake, and please, try not to use subsitutions. If you really cannot find buttermilk, stir a tablespoon of lemon juice into full-cream milk and let it stand to thicken. It's best to see this as a great creative effort, forget about fat and calories, and Just Do It, LOL!! The type of cocoa powder you use does not matter -- we only get Dutch process, and it makes the cake even more chocolatey. Don't refrigerate, it improves on standing. Just keep it in a cool place, covered. ADDED on May 11, after the disaster experienced by A & A's Mom! Not sure what happened there, but to prevent any chance of the cake breaking, either spoon on the ganache carefully, or pour on from the SIDES of the top layer. I confess I'm not sure how A & A's Mom's cake split like that!!