Preheat your oven to 350°F, grease an 8-inch square baking dish, or line it with parchment paper.

In a large mixing bowl, beat the butter and brown sugar together until light and fluffy, using a hand or stand mixer.

Add the egg, egg yoke, cookie butter, and vanilla extract and continue mixing, scraping the sides and bottom of the bowl until smooth and creamy.

Whisk the flour, white chocolate chips, and baking powder in a separate, small mixing bowl until combined.

Gradually add the dry ingredients to the wet mixture, stirring until combined. Do not overmix!

Spread the batter evenly into the bottom of the prepared baking dish and sprinkle the crushed Biscoff cookies on top.

Bake for 30-35 minutes until golden brown on top, crinkly on the edges, and a toothpick inserted in the center comes out clean. Do not overbake.

Let the blondies cool in the pan completely, about 1 hour, before slicing into squares and serving.

Enjoy your delicious Biscoff Blondies!