Ingredients

Instructions

• Preheat your oven to 325°F. Line rimmed baking sheets with unbleached parchment paper, and set them aside.

• Make the Cookie Dough. In a large bowl, place the flour, xanthan gum, cornstarch, confectioners’ sugar and salt, and whisk to combine well. Add the optional lemon zest, and whisk again to combine. Add the butter and then the egg, and mixing to combine after each addition. The dough will come together and should be smooth and relatively thick. Place the dough between two sheets of unbleached parchment paper and roll into a rectangle a bit more than 1/8 inch thick. Place the dough on a flat surface and place in the freezer until firm (5 to 7 minutes).

• Make the Filling. While the dough is chilling, make the filling. In the bowl of a stand mixer fitted with the paddle attachment, place the butter and beat on medium speed until light and fluffy. Add the salt, optional powdered lemon peel and confectioners’ sugar, and mix on low speed until the sugar is absorbed. Turn the mixer to medium speed and mix until the filling comes together (3 to 4 minutes). It will be very thick. Add 2 teaspoons milk, and mix on medium speed until the filling becomes smoother and creamier, but still thick. Add more milk if necessary to reach the desired consistency. Transfer the filling to a pastry bag fitted with a large piping tip (I used a large open star tip, like this one), and set it aside.

• Bake the Cookies. Once the cookie dough is chilled, cut out shapes using a 2 1/2 inch oval (or round) cookie cutter. Place the cutouts on the prepared baking sheets less than an inch apart from one another (they will not spread during baking). Place the baking sheets, one at a time, in the center of the preheated oven and bake, rotating once, until just beginning to brown around the edges (about 10 minutes). Remove from the oven and allow the cookies to cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.

• Assemble the Cookies.  Turn over half of the cookies, and pipe a generous amount of filling on each overturned cookie. Top with the remaining cookies to create sandwiches, pressing down gently to force the filling to the very edge of the cookies. Allow to sit at room temperature (or in the refrigerator) until the filling is set. Serve chilled or at room temperature.