For the cookies:
- 2 cups all-purpose flour
- 2 tablespoons cocoa powder
- ½ teaspoon baking powder
- ¼ teaspoon salt
- 8 tablespoons (1 stick, 1/2 cup) unsalted butter, at room temperature
- 1 cup light brown sugar, packed
- 1 large egg
- 1 teaspoon vanilla extract
- ½ cup buttermilk, at room temperature
- 1 ounce red food coloring
For the frosting:
- 8 ounces cream cheese, at room temperature
- 5 tablespoons unsalted butter, at room temperature
- 2 teaspoons vanilla extract
- 2 cups confectioners’ sugar, sifted
For the cookies:
Adjust oven rack to middle position; preheat oven to 375 F. Line baking sheets with parchment paper. In medium bowl, whisk together flour, cocoa, baking powder and salt.
In large bowl with an electric mixer, beat butter on medium-high speed for 30 seconds, until smooth. Add brown sugar and beat until light and fluffy, about 2 minutes. With mixer at medium speed, add egg and beat until thoroughly combined, then beat in vanilla. Add in flour mixture and buttermilk alternatively, starting and ending with buttermilk mixture. Fold batter with a spatula once or twice with rubber spatula to incorporate any remaining flour. Blend in food coloring.
Spoon (or pipe) tablespoonfuls of batter on prepared baking sheets, allowing 1 inch between each round.
Bake 7 to 9 minutes, or until tops are set. Cool completely on cookie sheets.
For the filling:
Add cream cheese and butter to mixer bowl and beat until smooth. Gradually add powdered sugar, alternating with vanilla. Beat until smooth.
To fill, dollop (or pipe) cream cheese filling on flat sides of half the cookies. Top with remaining cookies, flat sides down. Whoopie pies can be refrigerated in an airtight container up to 4 days. Let stand at room temperature 15 minutes before serving.