For a sinfully rich cake, you could try making peanut butter icing to top a devils food cake. The National Group provides a birthday cake for our employees each month. If there are 2 or more with a birthday in any given month, one of them gets to pick the flavor/kind of cake. November has only one birthday and that's Bryan's and this happens to be his favorite. Although I don't really bake cakes anymore, there isn't a bakery in town that does this, so I have made this cake for his birthday for several years. I think it's a bit too rich by itself, so I always provide some ice cream to accompany it.
(notice the different colors of the icing....that would be from the heat of my hand on the decorating bag, or I should say ziplock bag, which is what I used because I threw out all my vinyl decorating bags a long time ago. At 9:30 last night I wasn't about to go to the store to buy some, so I used practically a whole box of ziplock bags instead. They don't hold that stiff icing very well!
Some who hadn't tried it in previous years had some today and liked it, so that means that I may be making it more than once a year. Here is Bryan and his cake.