Traditional Whoopie Pies

Bahan-bahan (6 porsi)

• 2 cups all purpose flour
• 1/2 cup Dutch-processed cocoa powder
• 1 teaspoon baking soda
• 1/2 teaspoon salt
• 1 cup packed light brown sugar
• 1/2 cup (1 stick) unsalted butter, (at room temperature)
• 1 large egg, (at room temperature)
• 1 teaspoon vanilla extract
• 1 cup buttermilk
• 1/4 teaspoon instant espresso powder
• 1/2 cup (1 stick) unsalted butter, (at room temperature)
• 1 cup powdered sugar
• 1½ teaspoons vanilla extract
• dash of salt
• 2 (scant) cups Marshmallow Fluff or Creme