1. Mix flour, confectioners’ sugar, cocoa powder, 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 it 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 a 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 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. Warm the Biscoff spread slightly so it’s a bit softer and then spread a thin layer onto the cookies without an opening. Place the matching cookies with an opening on top and press together. Melt the milk chocolate glaze. Pour a small amount into the opening in the middle of the cookie sandwiches to cover the Biscoff spread. Before the chocolate sets, sprinkle some Speculoos cookie crumbs on top and let them dry completely. Store the cookies in a cookie tin without other cookies in a cool place. The cookies should stay fresh for at least a week (if stored correctly).