I, a lifelong denizen of the Pacific Coast, had never heard of Whoopie Pies until I read this article in the New York Times. For the uninitiated, Whoopie Pies are a homespun dessert staple in New England (particularly Maine) and in Pennsylvania Dutch country. As a thumbnail description, they are what Oreo Cakesters are attempting to replicate on a national scale. (But it goes without saying that the real Whoopie Pies are at least a thousand times more tasty.)
The classic Whoopie Pie is essentially some filling sandwiched between two large, cake-like cookies. It sounds not unlike a Moon Pie, but without the flavored coating. The traditional cookie is thick and dry and on the bland side, getting most of its flavor and texture from the sticky sweet filling. The filling can be made of either frosting or marshmallow fluff.