MAKES 36 WHOOPIE PIES
If your experience with whoopie pies has been limited to the kind sold in supermarkets, encased in a plastic wrapper with an expiration date stamped on the back, you’re in for a treat. These desserts are delicious, and perfect for a picnic since no utensils are required. The filling here is rich with vanilla (and the surprisingly perfect addition of flake sea salt), and the cake-like cookies that surround it are intensely chocolate.
This recipe makes a big batch but the “pies” freeze well. Having a dozen or so in the freezer means you’re ready with a special treat when the mood strikes.
FOR THE CAKES
⅓ cup bittersweet chocolate, chopped
¾ cup hot coffee
2½ cups all-purpose flour
1 cup cocoa powder
1 tablespoon baking powder
½ tablespoon kosher salt
1 cup (2 sticks) unsalted butter, softened
2 cups sugar
2 extra large eggs
1 tablespoon vanilla extract
1⅔ cups buttermilk
FOR THE SEA-SALT BUTTERCREAM
1 pound (4 sticks) unsalted butter, softened
1 cup marshmallow creme
3 cups confectioners’ sugar
2 tablespoons vanilla paste
2 teaspoons flake sea salt, such as Maldon salt
TO MAKE THE CAKES: Preheat the oven to 400°F.
Place the chocolate in a small bowl and pour the hot coffee over it. Stir gently with a fork as the chocolate melts; set aside and let cool to room temperature.
Combine the flour, cocoa, baking powder, and salt and set aside.
Using a mixer with the paddle attachment, beat the butter and sugar until very light and fluffy. Add the eggs one at a time and then the vanilla extract, beating until very light and airy. Add the chocolate-coffee mixture; combine thoroughly.
Add half of the flour mixture and half of the buttermilk; mix until well incorporated. Repeat with the remaining dry ingredients and buttermilk.
Line 2 baking sheets with parchment paper. Fill a piping bag fitted with a ½-inch round tip (or a 1-gallon sealable storage bag with a ½-inch hole cut in one corner) with one-third of the whoopie pie batter. Pipe 2-inch-wide circles, 1 inch tall, leaving at least 2 inches between them. (A standard-size baking sheet should hold a dozen per tray, three across and four down.)
Bake for 5 to 8 minutes, or until the cakes are just set. Transfer the sheets to a wire rack and let cool completely before removing the cakes with a spatula. Set the cakes aside and repeat piping and baking until all the batter has been used; you should end up with about 72 cakes, which will give you 36 filled whoopie pies.
TO MAKE THE SEA-SALT BUTTERCREAM: Using a mixer with the paddle attachment, beat the butter until light and fluffy. Add the marshmallow creme and beat again to combine. Slowly add the sugar, vanilla paste, and salt and combine thoroughly, then beat on high speed for 5 minutes.
Place one-third of the buttercream in a piping bag fitted with a ½-inch round tip (or a 1-gallon sealable storage bag with a ½-inch hole cut in one corner). Hold a cake flat side up and, starting in the center of it, pipe 1 to 2 tablespoons of buttercream filling over it evenly. Top gently with another cake; set aside and continue until all the cakes are filled, refilling the piping bag as you go. Serve.
NOTE: The whoopie pies may be stored at room temperature unless it is very warm, in which case they should be refrigerated. They may also be placed on parchment-lined baking sheets, wrapped tightly in plastic wrap, and frozen. Thaw at room temperature.