At least I've heard of this and I think I even had one once.
Whoopie Pies are also called black moon, GOB (a term used in the Pittsburgh area) or BFO for Big Fat Oreo. It can be classified as either a cookie (a real big one), pie or cake.
They are made of two round mound-shaped pieces of chocolate cake (and sometimes pumpkin or gingerbread cake) with a sweet creamy filling or frosting sandwiched in between. (Might they also be classified.
It is considered either a New England or Pennsylvania Amish tradition, but increasingly it is sold throughout the United States.
The name supposedly comes from when farmers would find one of these packed in their lunchbox, they's holler "Whoopie!!" There is some controversy as to its origin.
It is the Official State Treat of Maine.
I'd Show You a Picture of One, But You'd get Too Hungry. --RoadDog