What kind of frosting would taste good on Mississippi Mud Cake?

A ganache - 2 parts heavy cream, one part chocolate. The better the chocolate the better the ganache. I use my favorite dark chocolate chips and it always turns out amazing, also saves time chopping the chocolate. Heat your cream slowly on the stove top stirring often so you don't get a skin on top, once you see bubbles (boiling) pour on your chocolate. Let it stand 30-60 seconds. Take a spatula and stir, keep stirring until it's well blended, make sure you're scraping the sides and bottom. Let it stand until cooled. I've used the fridge to make it cool faster, but keep and eye on it, stir every 20 minutes and keep it well covered. Pour on your pie and enjoy.. mmm!! You can freze the remainder and make truffle balls, or add to your favorite buttercream recipe for a rich chocolate buttercream.