Double Chocolate Whoopie Pies
For the cakes
- 2 cups all-purpose flour
- 1/2 cup Dutch-process cocoa powder
- 1 1/2 teaspoons baking soda
- 1/2 teaspoon salt
- 1 cup sugar
- 1 stick (115 g) unsalted butter, softened
- 1 large egg, room temperature
- 1 teaspoon vanilla extract
- 1 cup buttermilk (or substitute)
For the filling
- 8 ounces (225 g) semisweet or bittersweet chocolate (I like 60-70 % cacao)
- 1 cup (240 g) heavy cream
- 1/8 teaspoon salt
For about 28 mini whoopie pies
For the cakes: Preheat oven to 350 F. Line two baking sheets with parchment paper.
Sift together flour, cocoa, baking soda, and salt in medium bowl; set aside. Beat sugar and butter with electric mixer on medium-high until light and fluffy, about 4-5 minutes. Add egg and vanilla, and beat until incorporated.
Stir in half of the flour mixture by hand, then half of the buttermilk, then repeat with the other half of the flour mixture and buttermilk. Stir until just combined, but do not overmix at this point.
Scoop generous tablespoons of batter 2 inches apart on baking sheets. Bake until cakes spring back when pressed lightly, about 10 minutes, rotating sheets halfway through baking.
Cool cakes on sheets for 10 minutes, then transfer to a wire cooling rack and repeat for remaining batter.
For the filling:
Coarsely chop chocolate. Bring cream to a boil over medium-high heat and immediately pour over the chopped chocolate. Add salt and let stand, undisturbed, for 10 minutes.
Stir with a whisk until smooth and shiny, scrape the sides and bottom of the bowl with a rubber spatula to incorporate all the chocolate.
Let ganache cool to room temperature, stirring often, 45 minutes to 1 hour. Beat it with a mixer on medium-high speed until fluffy and paler in color, 3 to 5 minutes. (This will yield about 2 cups.) Transfer to a disposable pastry bag with a large opening and use it as a filling for mini whoopie pies or spread it over cupcakes.
Transfer whipped ganache to a pastry bag with a fairly large opening. Pipe some ganache onto the flat sides of half the cookies. Sandwich with remaining cookies, pressing gently.
