Preheat the oven to 400C/350F degrees and line two baking sheets with parchment. Set aside.
Sift together the flour, cocoa powder, baking soda, and salt. Set aside.
In a mixing bowl fitted with a paddle, cream together the shortening and sugar.
Add the egg and vanilla and mix until combined.
Continue to mix on low speed while alternately adding the buttermilk and flour mixture. Stop to scrape the sides of the bowl with a rubber spatula as needed.
Spoon about ¼-cup of batter roughly 3 inches apart onto the prepared baking sheets (an ice cream scoop works well here).
Bake for 12-15 minutes or until the tops are puffed and a toothpick inserted into the center of one of the cakes comes out clean. Transfer to a wire rack to cool completely.
The Filling
Add all the ingredients to a large bowl and using the mixer paddle, beat until smooth.
Spread about 2 tablespoons of filling on the bottom side of one cake and top with another cake.
Wrap individually in cling film until you're ready to eat one.
Recipe by Orgasmic Chef at https://orgasmicchef.recipes/old-fashioned-whoopie-pies-recipe-from-maine/