Baked for the 2010 Serious Eats Cookie Swap
"I was going to make the Turtle Cookies from this same 2010 issue of a Cook's Illustrated, but the whoopies were much less work and seemed more festive. The peanut butter filling was inspired by my local Foodtown market, which for some appalling reason doesn't have marshmallow Fluff—the base for the filling in the original recipe." —Liz Gutman, SE chocolate columnist
Cake recipe adapted from 2010 Cook's Illustrated; Filling recipe adapted from Sky High, via Smitten Kitchen
- Yield:Makes about 28 mini whoopie pies
- For the Whoopie Pies:
- 2 cups flour
- 1/2 cup Dutch-process cocoa powder
- 1 teaspoon baking soda
- 1/2 teaspoon salt
- 1 cup packed light brown sugar
- 1 stick (8 tablespoons) unsalted butter, softened
- 1 large egg, room temperature
- 1 teaspoon vanilla extract
- 1 cup buttermilk (I used 1 cup milk with 1 tablespoon white vinegar added - let it sit for a minute, and you have buttermilk!)
- For the Filling:
- 6 oz cream cheese, room temperature
- 2 1/2 tablespoons butter, softened
- 3 cups confectioner's sugar
- 1/2 cup smooth peanut butter (preferably a commercial, homogenized brand)
- 2 teaspoons coarse sea salt
For the Cakes: Preheat oven to 350°F. Line two baking sheets with parchment paper.
Combine flour, cocoa, baking soda, and salt in medium bowl. Beat sugar and butter with electric mixer on medium-high till light and fluffy, about 4 minutes. Add egg and vanilla, and beat until incorporated. Reduce speed to low and alternate additions of flour mixture and buttermilk, mixing until fully incorporated after each addition.
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 15 minutes, then slide parchment onto wire cooling rack and repeat for remaining batter.
For the Filling: Sift confectioner's sugar to get out any lumps. Beat cream cheese and butter with electric mixer on medium-high speed until fluffy, about 3 minutes. Add confectioner's sugar one cup at a time, beating thoroughly between each addition and scraping the bowl down often. Add the peanut butter and salt and beat on high until fluffy, 2-3 minutes.
Spoon or pipe generous amount (about the size of a ping-pong ball) of filling onto half the cakes, then gently top with remaining cakes, pressing down gently to affix them. Can be refrigerated in an airtight container for up to three days.