- 1 3/4 cups unbleached all-purpose flour
- 3/4 cup unsweetened cocoa powder
- 1/2 teaspoon baking powder
- 1 cup granulated sugar
- 1 cup buttermilk, room temperature
- 1/2 teaspoon kosher salt
- 1 1/2 teaspoons baking soda
- 1/2 cup butter, softened
- 1 large egg
- 1 teaspoon pure vanilla extract
- 1/2 cup (1 stick) unsalted butter, room temperature
- 1/4 cup milk
- 3 to 4 cups powdered sugar
- 1/2 teaspoon pure vanilla extract
- Preheat oven to 400°F.
- Sift together flour, salt, cocoa powder, baking soda, and baking powder. Set aside.
- In the bowl of an electric mixer fitted with the paddle attachment, cream butter and sugar until light and fluffy. Add eggs, buttermilk, and vanilla. Beat until well combined. Slowly add flour mixture and mix until combined.
- If you have a whoopie pie pan, lightly grease, and using a one-tablespoon ice cream scoop, make the first 12 cookie halves. Bake at 400° for 10-12 minutes. Let cool on a cooling rack, then repeat for the other 12 cookie halves.
- If you do not have a whoopie pie pan, line two large baking pans lined with parchment, and using that same one inch scoop, place far enough apart so that they do not run into each other while baking.
- In the bowl of an electric mixer fitted with the paddle attachment, cream butter until smooth and creamy, 2 to 3 minutes. With mixer on low speed, add 3 cups powdered sugar, milk, and vanilla; mix until light and fluffy. If necessary, gradually add remaining cup of powdered sugar to reach desired consistency.
- Transfer buttercream to a disposable pastry bag and snip the end. When cookies have cooled completely, pipe 2 tablespoons buttercream onto the flat side of half the cookies. Sandwich with remaining cookies, pressing down slightly so that the filling spreads to the edge of the cookies.