Brownies!

Replace your white sugar with brown sugar, or add corn syrup (or both).

None sweet icing: Dilute your icing sugar with corn starch.

For the icing make a ganache or a butter/chocolate mixture. Look up ganache, it's just whipped cream with semisweet chocolate melted in it, then cooled. You can just spread it or whip it. otherwise melt about 3 parts semi sweet chocolate in a double boiler, remove from the water and add 2 parts butter, a little at a time beating so it melts. It will end up about the consistency of mayonnaise and you can spread it. If too hard, put back on the water a sec. If too soft, put over ice water a minute.
These are not very sweet

I find the cakey style brownies to be a bit less sweet. For icing...nothing could be simpler than a few handfuls of bitter or semi sweet chocolate chips tossed on the top of a pan of hot brownies. A quick spread around when all melted and there you have it! To gild the lily, toss some sprinkles on top of frosting when almost cooled. There are lots of really great colors and shapes available at the cake supply stores and Hobby Lobby and Michael's (even WalMart in hobby area).