Or if not BC, some other kind of icing that I can put under fondant.
You could ice the cake with chocolate ganache. They do that at Planet Cake, you can find them on youtube with covering a cake. You get a really smooth cake with it for covering. Also I think it would taste great with this kind of dark, mud chocolate cake.
If you don't like chocolate ganache you could always made a chocolate bc, just a simple one with melted chocolate (dark one) in it or cocoa powder.