Whoopie pies are a New England specialty that combines two soft cake-like cookies held together by a thick layer of frosting. The traditional version is chocolate with white frosting, but I wanted to start a new tradition with lemon whoopie pies. The light, moist, soft cookies look like the top of a muffin. They are filled with a thick layer of lemon cream cheese frosting and they deserve a great big whoop of delight.
An average lemon yields about 2 teaspoons of zest (the yellow part of the peel) and 3 tablespoons of juice; be sure to grate the zest before squeezing the juice. This cake-like batter releases easily from the buttered parchment paper.
makes 8 cookie sandwiches • cookie making 25 minutes • cookie baking 350 degrees, two baking sheets for about 12 minutes each
cookies
1½ cups unbleached all-purpose flour
½ teaspoon baking powder
¼ teaspoon baking soda
¼ teaspoon salt
6 tablespoons (¾ stick) unsalted butter, at room temperature
1 cup sugar
1 teaspoon finely grated lemon zest
1 large egg
1 tablespoon fresh lemon juice
1 teaspoon vanilla extract
½ cup buttermilk (any fat content is fine)
lemon cream cheese filling
6 tablespoons (¾ stick) unsalted butter, at room temperature
6 ounces cream cheese, at room temperature
1 teaspoon vanilla extract
1 teaspoon finely grated lemon zest
2 tablespoons fresh lemon juice
2¾ cups powdered sugar
Position a rack in the middle of the oven. Preheat the oven to 350 degrees F. Line two baking sheets with parchment paper and butter the paper.
MAKE THE COOKIES. Sift the flour, baking powder, baking soda, and salt into a medium bowl and set aside. In a large bowl, using an electric mixer on medium speed, beat the butter, sugar, and lemon zest until smoothly blended, about 1 minute. Stop the mixer and scrape the sides of the bowl as needed during mixing. Add the egg, lemon juice, and vanilla, mixing until blended, about 1 minute. The batter may look curdled. On low speed, add half of the flour mixture, mixing just to incorporate it. Mix in the buttermilk. Mix in the remaining flour mixture just until it is incorporated and the batter looks smooth again.
Drop heaping tablespoons (about 3 level tablespoons each) of dough onto the prepared baking sheets, spacing them 3 inches apart. Bake the cookies one sheet at a time until a toothpick inserted in the center comes out clean and the tops feel firm, about 12 minutes. With the exception of a thin line at the edges, the tops of the cookies should not brown. Cool the cookies on the baking sheets for 10 minutes, then use a wide metal spatula to transfer them to a wire rack to cool completely.
MAKE THE FILLING. In a large bowl, using an electric mixer on low speed, beat the butter, cream cheese, vanilla, lemon zest, and lemon juice until thoroughly blended and smooth, about 1 minute. Add the powdered sugar and mix until smooth, about 1 minute. If the filling is too soft to hold its shape, refrigerate until it is firmer, about 30 minutes.
Turn half of the cookies bottom side up. Leaving a ¼-inch plain edge, use a thin metal spatula to spread each one with about ¼ cup of filling. (An ice cream scoop with a ¼-cup capacity makes quick work of this.) Gently press the flat bottoms of the remaining cookies onto the filling.
Wrap each cookie in plastic wrap and refrigerate for at least 1 hour. Serve cold. The wrapped cookies can be stored in the refrigerator for up to 4 days.