I love Whoopie Pies, and grew up eating them in Massachusetts, but have not had great luck storing them, so I look forward to others' suggestions on that matter. I make small pies (3 cm in diameter) and use a recipe from Jane and Michael Stern that was published in Gourmet a long time ago. They use a regular butter-and-powdered-sugar frosting, rather than the Fluff that is supposedly traditional in the New England version.

I posted the recipe on another site:
http://www.recipezaar.com/recipe/Whoopie-Pies-67828Good thing, my Gourmet magazines are in the attic. Also, it seems that epicurious does not have the old recipe, which uses vegetable shortening, but has a butter recipe that looks quite good.
http://www.epicurious.com/recipes/food/ ... ies-107615Maybe time for a whoopie pie tasting.
Cheers, Jen