So, my brother (read "room-mate" because I deny relation to someone this stupid on principal) thought that you could turn a chocolate bar into a brownie by microwaving it. Of course, he was incorrect as to the accuracy of that assumption and now my microwave smells like the litter-box of a cat who gorged itself on godiva. I've tried cleaning it several times to no avail. All of my food has this really subtle but still noticeable taste of burnt chocolate to it and it's getting a bit annoying. Any suggestions on how to correct this problem? Thanks in advance.

EDIT: I thought I should mention that I tried googling various things, and the odor of my microwave has gotten slightly worse, but with a hint of coffee to boot. Boiling a large bowl of water for about 10 minutes didn't seem to have any affect and neither did a past of baking soda and water seem to help either. I was reluctant to try borax since that is not really anything I want near or around food.