Christmas Cookies

In an electric mixer, beat the butter with the sugar and a pinch of salt until creamy. Beat in the egg yolks, lemon zest and vanilla. On low speed, beat in the flour, 1 cup at a time, until just combined. Divide the dough into 4 equal pieces and flatten them into smooth disks. Wrap separately in wax paper and refrigerate until firm, at least 30 minutes, or for up to 2 days; or freeze for up to 1 month.

Preheat the oven to 350 degrees F.

On a lightly floured surface, roll 1 disk of the dough 1/8 inch thick. Using cookie cutters, cut the dough into star and moon shapes. Use mini cutters to stamp out patterns in half of the cookies and decorate with sprinkles. With a metal spatula, transfer the cookies to a large cookie sheet lined with parchment paper. Bake for 15 to 20 minutes, until pale golden. Let the cookies cool on the parchment, then transfer to a rack to cool completely. Repeat with the remaining disks.

Spread a rounded teaspoon of jam on each of the solid cookies and top each with a decorated cookie.

MAKE AHEAD:
The cookies can be stored for up to 3 days in an airtight container.)