Red velvet cake, once a minor curiosity, is now ubiquitous in American bake-shops. It is a trend that outlasted its trendiness. Though most closely identified as a Southern recipe, the red velvet probably originated somewhere in the Northeast as a cocoa powder- and buttermilk-based cake. In theory, the cocoa powder reacts with the baking soda to create a reddish hue, but somewhere along the way, the red quotient began to be upped with an unhealthy dose of red dye. Unfortunately, a rash of basic vanilla cakes containing buckets of red dye suddenly became “red velvet cakes.” True red velvet needs at least three ingredients to qualify for the moniker: cocoa powder, buttermilk, and shortening (it lends a great fluffy texture). I include all of these in our Red Velvet Whoopie Pies, and fill them with a delectable cream cheese frosting. It is a Southern/Northern hybrid that looks great and tastes even better.