1. Mix flour, confectioners’ sugar, and salt in a bowl. Add the cold butter in small pieces, the egg yolks, and the vanilla extract. Knead with the dough hooks of a hand mixer (or use your hands) until you get a nice and smooth dough. Wrap it in plastic wrap and place it in the fridge for about 1 hour.

2. Preheat the oven to 200°C (390°F). Line a baking sheet with baking parchment. Divide the dough into 14-15 portions and shape each one into a small ball. Place the balls with some space in between on the prepared baking sheet. Flatten them slightly and then press your thumb (or the end of a wooden spoon) into the dough to create an indention for the filling later on. Brush the dough pieces with some milk and sprinkle with the Biscoff cookie crumbs. Bake the cookies for about 8-10 minutes – they will not get very dark. Remove from the oven and let the cookies cool down on a wire rack.

3. Warm the Biscoff spread briefly in the microwave until it has become soft and runny. Pour the runny spread (e.g. with a small spoon) into the indentions in the cookies and let cool down and set again. Store the cookies in a cookie box at room temperature.