I received a wonderful birthday present from my in-laws last week. I ate these for the first time in Cape Cod and could not get enough. They are called Whoopie Pies!! Imagine an Oreo cakester but 10x more delicious.
I have seen a lot of places offer them now and even more recipes but you can't beat the chocolate whoopie pies from http://www.stevessnacks.com/. Order a dozen, or 2, you will not regret it.