¾cup(1 1/2 sticks) unsalted butter, room temperature
4 ½cupspowdered sugar, sifted
6tablespoonsBaileys Irish Cream Liqueur, or until desired consistency
Chocolate Whoopie Pies
Preheat oven to 350° F. Line a baking sheet with parchment paper and set aside.
In a medium bowl, whisk together the flour, cocoa, baking soda, espresso powder and salt. Set aside.
In the bowl of a stand mixer (or using a hand mixer), cream together the butter and brown sugar, about 1 minute. Add the egg and vanilla extract and beat until light and creamy, about 2 minutes.
Add dry ingredients to butter mixture in three parts, alternating with buttermilk (so add one third flour mixture, half cup buttermilk, another third flour mixture, half cup buttermilk and finish with remaining flour mixture). Combine well after each addition.
Transfer batter to a frosting bag fitted with a round tip.* Pipe batter into circles two inches in diameter on the prepared baking sheet (each about three inches apart as they will spread slightly). Bake until tops are puffed and cakes spring back when touched, 10 to 12 minutes. Remove from oven and cool completely before filling.
Bailey's Buttercream Filling
In a bowl with a mixer, cream together butter, Baileys, and powdered sugar. Spoon frosting into a pastry bag fitted with desired tip and pipe it generously on flat side of the cakes. Top filled half with another cake to sandwich the buttercream. Store in an airtight container at room temperature for up to 3 days.
*Alternatively, you can spoon batter onto the cookie sheet and use the spoon (or your fingers) to shape them into circles.