Homemade Whoopie Pies

Ingredients:

For the cakes:

1 cup all-purpose flour

1 cup whole-wheat pastry flour

1/2 cup unsweetened cocoa powder

1 teaspoon baking soda

1/2 teaspoon baking powder

1/4 teaspoon salt

1/2 cup light olive oil

1 1/4 cups packed brown sugar

2 egg whites

1/2 cup spinach puree (see note below)

2 teaspoons pure vanilla extract

1/2 cup low-fat (1%) buttermilk

Nonstick cooking spray

For the filling:

1 stick (1/2 cup) unsalted butter, softened

1 1/4 cups confectioners’ sugar

2 cups marshmallow cream

1 teaspoon pure vanilla extract

Directions:

Preheat the oven to 350°F. Whisk together the flours, cocoa, baking soda, baking powder and salt in a bowl or shake in a zipper-lock plastic bag until combined.

In a large bowl or standing mixer, beat the oil and brown sugar with an electric mixer at medium-high speed until well combined. Add the egg whites and mix on low until well blended. Blend in the spinach puree and vanilla.

Alternately add in the flour mixture and the buttermilk, beginning and ending with flour, mixing until smooth and just combined.

Coat 2 large baking sheets with cooking spray. Place tablespoonfuls of batter about 2 inches apart onto baking sheets. Bake until the cakes are cooked through and spring back to the touch, 8 to 10 minutes. Transfer to a rack to cool completely.

Make the filling. With an electric mixer on medium speed, beat together all the ingredients until smooth, about 2 minutes. Spread a rounded tablespoonful of filling on the flat sides of half of the cakes and top with the remaining cakes.