I wanted a childhood favourite called "Whoopie Pies" (a New England treat -- the rest of the U.S. hasn't heard of them). Basically it's chocolate cake, baked in little mounds, filled with butter-cream. I think they're named that because kids always yell, "Whoopie!" when they know mum is making them.
Here's the most authentic recipe I found online -- just substitute your GF flour (and in my case, milk as well) for the regular flour. (Steer clear of those recipes using marshmallow fluff in them! Not authentic!)