Whoopie pies have been around for a long time.  They deserve to be. 

They're two cake-like cookies sandwiched together and filled with frosting, whipped cream, or a pastry filling. 

They're simple to make, usually made with a cake mix batter scooped on a cookie sheet.  Usually you have to tinker with the cake mix to get the right consistency but we'll give you a deal on the mix.