One-Bowl Gingerbread Whoopie Pies

Directions

1. Put oil, brown sugar, vanilla and molasses in a stand mixer bowl or mixing bowl and whisk to combine. (Pro Tip: You'll be making the whoopie pie batter and frosting in the same bowl, so even though you're not using a mixer just yet, start with a stand mixer bowl -- you'll be using the mixer later.)
2. Add eggs and yolk 1 at a time, whisking after each addition. Add buttermilk and whisk again.
3. Put a sheet of parchment paper or a plate on a work surface and sift flour, baking powder, baking soda, salt, and spices onto it, using a fine strainer. Add dry ingredients to wet in 3 additions, folding them together until well-blended. (Pro Tip: If you have it, parchment paper is a handy tool for one-bowl baking; you can use it not only for lining a pan, but also to use as a landing pad when sifting dry ingredients.)