Gluten-Free Whoopie Pies

Ingredients

• For the cookies:
• Dry Ingredients
• 4 ounces white rice flour
• 2 3/4 ounces sweet rice flour
• 1 1/2 ounces Dutch-process cocoa powder
• 2 1/4 ounces tapioca starch
• 1 1/4 teaspoons baking soda
• 1 teaspoon salt
• 1/2 teaspoon xanthan gum
• Wet Ingredients
• 4 ounces unsalted butter, room temperature
• 7 ounces dark brown sugar
• 1 large egg
• 1 teaspoon vanilla extract
• 1 cup buttermilk
• For the filling:
• 4 ounces butter, softened
• 1 jar marshmallow crème
• 3/4 cup confectioners' sugar

Directions

1. For the cookies, place an oven rack in the middle of the oven and heat it to 350 degrees F. Cover a baking sheet with parchment paper and keep it nearby.
2. In a small bowl, whisk the white rice flour with the sweet rice flour, then add the cocoa powder, tapioca starch, baking soda, salt, and xanthan gum and whisk again until the dry mixture looks even.
3. Set up a stand mixer with the paddle attachment. Add the butter and brown sugar to the mixer bowl and beat until the mixture becomes a little lighter, about 1 minute. Use medium high-speed for a stand mixer, or high speed if you are working with a handheld mixer. Stop the mixer and scrape the bowl well, getting the sides and bottom. Add the egg and vanilla extract, then start the mixer again and beat until the egg is fully blended in, about 1 minute. Scrape the sides and bottom again, then mix for 15 seconds more.
4. Add 1/3 of the dry mixture and mix just until it disappears into the batter. Pour in half the buttermilk and mix until smooth. Add another 1/3 of the dry mixture and mix until combined. Mix in the remaining buttermilk, then add the rest of the dry mixture. Beat until the batter is thick and smooth, about 30 seconds.
5. Scoop 6 portions of batter, about 1/4 cup each, onto the prepared baking sheet. Leave several inches between them, because they will spread in the oven.
6. Bake until the cookies are firmed up and bounce back when gently pressed, about 18 minutes.
7. Take the pan out of the oven and leave the cookies on it for 1 minute. With a metal spatula, move them to a wire rack to cool. Continue the same baking process with the rest of the batter.
8. As the cookies cool, prepare the filling. Once the cookies are cool, spread the icing between them to make sandwiches.
9. For the filling, beat the butter and confectioners’ sugar in a medium mixing bowl until fluffy and pale, about 30 seconds. Use high speed with a handheld mixer, or medium-high speed with a stand mixer.
10. Add the marshmallow crème and vanilla. Beat until the filling is fluffy.