If you’ve never had a fluffernutter, you haven’t really lived. Today, to my astonishment, I learned that some people don’t know what a fluffernutter is…and even if they knew, they’d never actually had one. How is this possible? This is America. Land of the marshmallow fluff, home of the peanut butter.

But seriously, if you’ve neither heard of nor eaten a fluffernutter, it’s a sandwich made with white bread, peanut butter, and marshmallow creme (or fluff, if you will)…and it is delicious. Invented in Massachusetts during World War I, this fluffy, peanut buttery treat was originally called a liberty sandwich, though I have no idea why. Last weekend I tried (unsuccessfully, but that’s another story for another time) to make fluffernutter cupcakes; they failed, but these flutternutter whoopie pies were a huge hit in my office today. The recipe below is adapted from Baking Bites, though I used a different type of filling instead of just marshmallow creme and peanut butter. This recipe makes 18 whoopie pies, and next time I think I’ll use a smaller cookie scoop to yield more.

Ingredients

For the peanut butter whoopie pies

• 1 3/4 cups flour
• 1/2 teaspoon baking powder
• 1/2 teaspoon baking soda
• 1/4 teaspoon salt
• 8 tablespoons unsalted butter, at room temperature
• 1/2 cup sugar
• 1/2 cup light brown sugar
• 2 eggs
• 1/2 cup peanut butter
• 1 cup sour milk* or buttermilk
• 1 teaspoon vanilla extract

*To make sour milk, place 1 tablespoon vinegar in a glass measuring cup and add enough milk to equal 1 cup total. Stir; let stand for 5 minutes before using.

For the fluffy white filling

• 8 tablespoons unsalted butter, at room temperature
• 1 7-ounce jar marshmallow creme
• 2 1/2 teaspoons vanilla extract
• 2 3/4 cups powdered sugar

Preparation

Preheat oven to 350 degrees. Line three baking sheets with parchment paper.

In a medium bowl, combine flour, baking powder, baking soda, and salt; set aside.

In a mixing bowl, cream butter and sugars until light and fluffy. Add eggs, one at a time, scraping the sides of the bowl well. Add peanut butter and beat to combine, then add vanilla and beat well.

Add flour mixture and sour milk alternatively, beginning and ending with the flour, beating until no dry streaks remain and batter is well-combined. Your batter will look more like cake batter than cookie dough.

Using a 2-inch cookie scoop, drop scoops of batter onto prepared sheets; you should be able to fit 6 cookies on each sheet, as they will spread.

Bake for 12-14 minutes, until cookies are set and the tops spring back when lightly pressed. Remove from oven and cool on baking sheets for a few minutes, then remove to a wire rack to cool completely before filling.

To make the filling, place butter in a mixing bowl fitted with a paddle attachment and beat on medium speed for 1-2 minutes. Add marshmallow creme and vanilla and beat until very well-combined.

Add powdered sugar about 1 cup at a time, beating well between each addition and scraping the sides of your bowl frequently. You want a firm but spreadable consistency so that your filling doesn’t ooze out the sides.

Flip cookies over. Using a 1-inch cookie scoop, drop generous scoops of filling onto half of the cookies. Using a small offset spatula, spread filling slightly, then place another cookie on top.

Wrap each whoopie pie in plastic wrap for easy serving and storage. Since they are so large, it’s nice to be able to eat half of one and save the other half for later.