1/2 cup butter, softened
1 cup brown sugar
1 teaspoon vanilla extract
2 cups all purpose flour
1/3 cup cocoa powder
1 teaspoon baking powder
1 teaspoon baking soda
1/2 teaspoon salt
1 cup buttermilk
Whoopie Pie Filling
Preheat oven to 350 degrees F. Lightly spray Whoopie Pie Pan with nonstick cooking spray.
In a large bowl, beat butter and sugar with electric mixer on medium speed until light and fluffy, 3 minutes. Add egg and vanilla; beat until well combined.
In another bowl, sift together the flour, cocoa, baking powder, baking soda and salt. Add half the dry ingredients into the butter mixture and mix on low speed. When dry ingredients are almost incorporated, stop the mixer and add the buttermilk. Continue to mix on low speed until all the ingredients are almost incorporated. Stop the mixer and add the remaining dry ingredients. Mix on low until just combined. Spoon 2 tablespoons of batter into each cavity; spread batter to the edges. Cavity should be about 2/3 full.
Bake for 8-10 minute. Allow cakes to cool in pans 8 minutes. Remove and cool completely before filling. To assemble pies spread filling on one cake and sandwich with another cake.
Makes 12 whoopie pies (24 cakes total).