Clementine Thumbprint Cookies | TASTE

Make the curd: In a small saucepan, combine the sugar and zest and rub together with your hands until very fragrant. Add the egg yolks and cornstarch and whisk until a thick paste is formed. Slowly whisk in the citrus juices, then place the pan over medium-low heat. Cook, whisking constantly, until the mixture thickens and begins to bubble, about 5 minutes. Whisk the mixture vigorously and let boil for 1 minute, then remove from the heat and stir in the butter until smooth. Transfer to a medium bowl and cover with plastic wrap pressed directly to the surface. Use immediately or chill for up to 3 days. Make the cookies: Position a rack in the center of the oven and heat to 350°F. Line two large cookie sheets with parchment paper and set aside. In the bowl of a stand mixer fitted with the paddle attachment, combine the butter, both sugars, zest, and salt and beat on medium-high speed until smooth and creamy, about 3 minutes. Add the yolks and vanilla extract and continue mixing until well combined, taking care to scrape down the sides of the bowl as needed. Finally, add the flour and mix on low speed until just combined. Form the dough into smooth 1-inch balls and place them, evenly spaced, on the two cookie sheets. It’s recommended to bake one pan at a time. Bake on the center rack until the cookies begin to puff and expand, about 5 minutes, then remove the pan from the oven. Use a ½-teaspoon measure to press a deep indent in the center of each cookie—be careful as the pan will be very hot. Fill each indent with about ½ teaspoon of curd, then return the pan to the oven and bake until the cookies are dry to the touch and just barely beginning to turn golden around the edges, 5 to 6 minutes more. The cookies will still be pale and soft but will set up as they cool. Let cookies cool on the pan, then dust with powdered sugar. Store cookies in an airtight container at room temperature for up to 4 hours, or in the refrigerator for up to 4 days. Both the cookie dough and the curd can be made ahead of time. The cookie dough balls can be stored in an airtight container and frozen for up to 3 months. The dough can be baked directly from the freezer—just be sure to add a few extra minutes to the first half of the baking time, or the cookies will still be frozen in the center when you try to fill them. The curd cannot be frozen but can be made up to 3 days in advance and stored in the refrigerator until ready to use.