1¼ cups (2½ sticks) unsalted butter, slightly softened
6 egg yolks
1½ cups confectioner’s sugar
1 teaspoon baking powder
3 cups all-purpose flour
1 lemon, juiced
1½ cups raspberry or apricot jam
Additional confectioner’s sugar for dusting
Line two cookie sheets with parchment paper or silicone baking mats and set them aside.
In the bowl of a stand mixer fitted with a paddle attachment, beat the butter and egg yolks at medium speed until well blended. Add the confectioner’s sugar and continue to beat until the mixture turns much lighter in color.
Stir the baking powder into the flour, and then add flour to the batter. With the mixer on low speed, add the lemon juice. Continue to beat on low speed until well incorporated.
Remove the dough from the mixer and, with a sturdy spatula, fold the dough together. Sprinkle with a little flour to make it less sticky. Form the dough into a ball, wrap with plastic, and refrigerate for one hour.
Heat the oven to 300 degrees F. Remove the dough from the refrigerator, unwrap, and knead it on a well-floured surface. Once it’s workable, roll the dough out to ¼-inch thickness.
Use a cookie cutter to cut out the cookie tops and bottoms. If your cookies will have a decorative window cutout, you’ll need a smaller circle cutter for every other cookie.
Arrange the cookies on the prepared baking sheets and bake for 12 to 15 minutes. Cookies should be creamy in color, with just a tinge of golden color at the edges. If not, put them back in and keep checking every two minutes until they’re done. Remove the cookies to a wire rack to cool, keeping cutout ones (the tops) face up and together, solid ones on their own.
Dust cutout cookies, the tops, with confectioner’s sugar.
Spoon a small amount of jam on the “back”side of a solid cookie (the part that was against the cookie sheet), and top with a dusted cutout cookie to form a sandwich. These can be stored in a airtight container for up to three weeks.