In a large mixing bowl, beat the softened butter until smooth and creamy.

Gradually add the all-purpose flour and mix until just combined.

Continue mixing until the mixture becomes light and crumbly.

Add the granulated sugar and brown sugar. Beat until the mixture is light and fluffy.

Add the egg yolks and vanilla extract. Mix until smooth and fully incorporated.

Add the Biscoff cookie butter. Beat until the cookie butter is evenly incorporated into the mixture.

Add the remaining all-purpose flour, baking powder, baking soda, and salt.

Fold everything together using a spatula until a soft cookie dough forms.

Cover the dough and refrigerate for 20–30 minutes.

Scoop equal portions of dough onto a parchment-lined baking sheet, leaving about 2 inches of space between each cookie.

Bake in a preheated 350°F (175°C) oven for 10–12 minutes, or until the edges are lightly golden.

Allow the cookies to cool on the baking sheet for 5 minutes, then transfer them to a wire rack to cool completely before serving.