Buy one here
Ana, from Gail's comments :
Whoopie Pie. Two very large chocolate cake muffin top thingies. About the size of large pancakes. The flat part of these are slathered with chocolate ganache. Sandwiched between these two discs of hell is a thick layer of heavily sugared whipped cream.
Ohmygod.
Ana ate so much of one of the above pictured treats, that she feels sick today. I'd never heard of 'em, but -bless the intertubes- now I have.
History from What's Cooking America:
Whoopie pies are considered a New England phenomenon and a Pennsylvania Amish tradition. They're one of Maine's best known and most loved comfort foods. Mainers will even claim that they were weaned on whoopie pies. In Maine, these treats are more like a cake than a pie or a cookie, as they are very generously sized (about hamburger size). they're so hug that you'll want to share one with a friend. A big glass of milk is almost mandatory when eating a whoopie pie.
A whoopie pie is like a sandwich, but made with two soft cookies with a fluffy white filling. Traditional whoopies pies are made with vegetable shortening, not butter. The original and most commonly made whoopie pie is chocolate. but cooks like to experiment, and today pumpkin whoopie pies are a favorite seasonal variation.
the recipe for whoopie pies has its origins with the Amish, and in Lancaster county, Pennsylvania, it is not uncommon to find roadside farm stands offering these desserts. Amish cooking is about old recipes that have fed families for generations, with no trendy or cross-cultural fusions or mixtures. These cake-like whoopie pies were considered a special treat because they were originally made from leftover batter. According to Amish legend, when children would find these treats in their lunch bags, they would shout "Whoopie!"
Recipe is at the link as well.