Whoopie pie

The whoopie pie, alternatively called a black moon, gob , black-and-white, bob, or BFO (for Big Fat Oreo), is an American baked confection that may be considered either a cookie, pie, sandwich, or cake. It is made of two round mound-shaped pieces of usually chocolate cake, or sometimes pumpkin, gingerbread or other flavored cakes, with a sweet, creamy filling or frosting sandwiched between them. While considered a New England classic and a Pennsylvania Amish tradition, they are increasingly sold throughout the United States.

Source: Wikipedia