Whoopie Pie Recipe

Preheat and prepare pans

Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone baking mats. Set aside.

Cream butter and sugars: In a large bowl or stand mixer fitted with the paddle attachment, beat the 0.75 cup softened butter, 0.75 cup packed brown sugar, and 0.25 cup granulated sugar on medium speed until light and fluffy, about 2–3 minutes. Scrape down the bowl as needed.

Add egg and vanilla: Add the egg and 1 tsp vanilla extract and beat until fully incorporated, about 30 seconds.

Combine dry ingredients: In a separate bowl, whisk together 1 cup all-purpose flour, 1.25 cups rolled oats, 0.5 tsp baking soda, 0.5 tsp ground cinnamon, and 0.25 tsp salt until evenly distributed.

Mix dry into wet: Reduce the mixer speed to low and gradually add the dry ingredients to the butter mixture. Mix just until a uniform, slightly sticky cookie batter forms, about 20–30 seconds. Do not overmix.

Spoon and shape: Using a small cookie scoop or tablespoon, portion batter into 1-tablespoon rounded mounds (about 18–20 mounds total). Place them on the prepared baking sheets about 2 inches apart. Flatten each mound gently with the back of a spoon to form disks approximately 2 to 2.5 inches in diameter — these will spread minimally.

Bake: Bake in the preheated 350°F (175°C) oven for 10–12 minutes, or until edges are set and the centers appear slightly soft. Rotate pans halfway through baking for even color.

Cool: Remove sheets from oven and allow cookies to cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely. Cookies must be fully cool before filling to prevent filling from melting.

Beat butter: In a medium bowl or the stand mixer bowl (clean), beat 0.5 cup softened butter on medium speed until smooth, about 1 minute.

Add sugar: Gradually add 2.5 cups confectioners' sugar, about 1/2 cup at a time, beating on low after each addition until incorporated to avoid a sugar cloud. Once added, increase speed to medium and beat until smooth and fluffy, about 1–2 minutes.

Add marshmallow and flavor: Add 0.5 cup marshmallow creme, 1 tsp vanilla extract, and 0.125 tsp salt. Beat on medium until incorporated.

Adjust texture: Add 1 tablespoon milk or heavy cream and beat 20–30 seconds. If filling is too stiff, add additional 1 teaspoon of milk at a time until spreadable but pipeable. If too thin, add a little more confectioners' sugar, 1–2 tablespoons at a time.

Assemble whoopie pies: Pair cooled cookies by size. Using a small offset spatula or piping bag fitted with a plain round tip, place about 2 tablespoons of filling on the flat side of one cookie and gently sandwich with a matching cookie. Press together until filling reaches the edge but not overflowing. Repeat with remaining cookies.

Set and store: For best texture, place assembled whoopie pies on a tray and refrigerate uncovered for 20–30 minutes to let the filling firm slightly. Store whoopie pies in an airtight container at room temperature for up to 2 days or refrigerated for up to 5 days. If refrigerated, bring to room temperature 15–20 minutes before serving.