The critical step in making whoopie pies is to wrap them individually in plastic wrap, whether they are to be frozen or eaten fresh. Left unfrozen, they improve with a little age: If you can stand to wait for 2 days, the wrapped and refrigerated cookies will be moister and more delicious. But after about 4 days, they might begin to taste stale.
Make Ahead: When individually wrapped and stored in an airtight container, the whoopie pies may be frozen for 1 month.
Servings: 33 2 1/2-inch cookie sandwiches
- For the cookies
- 4 cups flour
- 1 cup good-quality unsweetened cocoa powder
- 2 teaspoons baking soda
- 1 teaspoon baking powder
- 1 teaspoon salt
- 1 cup low-fat buttermilk
- 1 cup water
- 1 teaspoon vanilla extract
- 8 ounces (2 sticks) unsalted butter, at room temperature
- 2 cups sugar
- 2 large eggs, plus 2 large egg yolks
- For the filling
- 16 ounces (4 sticks) unsalted butter, at room temperature
- 1 cup confectioners' sugar
- 1/2 teaspoon salt
- 4 ounces good-quality white chocolate, melted and cooled to about 93 degrees (best to use some from Biagio Fine Chocolate, with at least 30 percent butterfat)
- 1/2 teaspoon vanilla extract
For the cookies: Position oven racks in the upper and lower thirds of the oven; preheat to 350 degrees. Line several baking sheets with parchment paper.
Combine the flour, cocoa, baking soda, baking powder and salt on a large sheet of wax paper or parchment paper.
Combine the buttermilk, water and vanilla extract in a liquid measuring cup.
Combine the butter and sugar in the bowl of a stand mixer (preferably using a paddle attachment) or an electric hand-held mixer. Beat on medium speed for several minutes, until light and fluffy. Reduce the speed to low; add the eggs and egg yolks one at a time, beating until incorporated between each addition, then alternate additions of the flour and buttermilk mixtures until well combined.
Portion the cookie dough in 2-tablespoon amounts on the prepared baking sheets, spaced 2 inches apart. Make about 66 mounds of equal size. Bake 2 sheets at a time (on the upper and lower oven racks) for about 6 minutes, then rotate the sheets top to bottom and front to back; bake for 6 to 8 minutes, until the cookies are set, but springy to the touch. Ttransfer to wire racks to cool completely.
While the cookies are cooling, make the filling: Combine the butter, confectioners' sugar, salt and vanilla extract in the bowl of a stand mixer (preferably with a paddle attachment) or an electric hand-held mixer. Beat on low, then medium-high speed until creamy and smooth. Stop to add the melted, slightly cooled chocolate; beat on low speed until just combined.
To assemble, place a tablespoon or two of the filling on the flat sides of half of the cooled cookies. Press the flat sides of the remaining cookies on top of the filling to make the cookie sandwiches.
Wrap each whoopie pie individually in plastic wrap, then transfer to an airtight container.
From chef Karen Urie of the Town House restaurant in Chilhowie, Va.
Tested by Melissa McCart and Jane Touzalin.
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