For the Cookies

1. Preheat your oven to 350 degrees Fahrenheit. Line baking sheets with parchment paper to ensure the cookies come off of the pan cleanly after baking.
2. In a large bowl with a hand mixer or in the bowl of a stand mixer that is fitted with a paddle attachment, beat room temperature butter on medium speed until smooth.
3. Add egg yolk and vanilla to the butter and mix until combined. Scrape down the sides and the bottom of the bowl and continue mixing to ensure the ingredients combine properly.
4. With the mixer on low speed, add all purpose flour, powdered sugar, and salt to the batter. Mix on low speed until combined. The mixture will look extremely dry as it comes together. Be patient and continue mixing, but do not mix past when the dough comes together and all of the dry ingredients disappear.
5. Roll the dough onto a floured surface or baking mat using a rolling pin or wine bottle. Roll the dough to be about 1/8 inch in thickness.
6. Using a 3 inch round cookie cutter or a cup and knife, cut the dough into circles. Combine the leftover scraps into a ball and repeat the process of rolling out the dough and cutting it. Only re-roll the dough once for best results. You should have about 36 circles of dough.
7. Using a linzer cookie insert, backside of a piping tip, or a knife, cut a portion of the center out of half of the dough circles.
8. Ensure that full cookies and cookies with the centers taken out are baked on separate baking sheets, as the cookies with a cut-out in the center will require less baking time.
9. Bake cookies for 9-12 minutes until the cookies are light on top and just starting to turn light golden brown around the edges. The bottoms of the cookies should look golden in color when lifted from the pan with a spatula.
10. Allow the cookies to cool before decorating and assembling.

For Assembly and Decoration 

1. Place the cookies with the cut-out centers on a piece of parchment paper, paper towel, or baking sheet. Place powdered sugar into a sifter and sift over the cookies.
2. Microwave the jam for 10 seconds or heat in a small saucepan until smooth. Transfer the jam to a piping bag, parchment triangle, or Ziploc bag with the corner cut off for ease.
3. Pipe about 1/2 tablespoon of smooth jam into the center of each of the uncut cookies. Try to keep the jam as close to the center as you can to prevent the jam from spilling out the sides.
4. Top each of the jam-covered cookies with one of the powdered sugar cut-out cookies. Allow the cookies to set if possible. Store at room temperature tightly covered or in an airtight container for up to 5 days. Cookies will soften over time.