1. Mix flour, confectioners’ sugar, and salt in a large bowl. Add the butter and egg yolk and knead everything with the dough hooks of a hand mixer (or your food processor) until smooth. Wrap the dough in plastic wrap and place in the fridge for about 30-45 minutes.

2. Preheat the oven to 350°F (180°C). Line a baking sheet with baking parchment and set aside. Roll out half of the dough thinly on a lightly floured surface, then cut out round cookies (with cookie cutter or a glass). Cut out the center of half of these cookies with a smaller round cookie cutter/glass and place all of them on the baking sheet. If you have more space and leftover dough roll out again and cut out more cookies. Place the remaining dough in the fridge again and bake the first batch of cookies for about 9-10 minutes in the preheated oven. The cookies should not get much color. Take out and let cool down on the baking sheet for a moment, then transfer to a wire rack and let cool down completely. Repeat with the remaining dough until all dough is used, and you got the same amount of cookies with/without a cut-out center.

3. For the decoration mix the confectioners’ sugar with some lemon juice until smooth. You want the mixture to be on the thicker side and spreadable, not too runny. Coat the cookies with the cut-out center with the glaze and sprinkle with the nonpareils. Let dry completely.

4. Stir the jam to loosen it up (you can also warm it up briefly), then add about 1 tsp. on each cookie (the ones without sprinkles), smooth it out a bit, and press a colorful cookie with an opening on top to create a sandwich cookie. There you go, you’re done! You can try one (!) cookie now. Let the rest dry for at least 1 hour. Store in a metal box or similar in a cool place without other types of cookies. When stored correctly the cookies should be good to eat for at least 7-10 days.