Marble cake made with cake mix, flour, sugar and other ingredients to make it more like scratch.
For the frosting, make sure all ingredients are at room temperature and not cool at all. If ingredients are too cool, some of the chocolate may re-solidify giving you little chunks of chocolate in the frosting. It's happened to me a couple of times. People actually like the little chunks, but I don't think the frosting looks as nice when that happens.