Preheat your oven to 350°F (175°C). Grease a 9"x9" baking pan with butter or cooking spray, then line it with parchment paper. Set aside.

In a medium saucepan over low heat, melt the butter until fully liquid. Remove from heat and cool slightly. In a large bowl, whisk together melted butter, cookie butter, brown sugar, and granulated sugar until smooth.

Add the eggs and vanilla extract to the mixture and whisk until fully blended without streaks of egg visible.

In a separate bowl, combine flour, baking powder, salt, and cinnamon. Gradually add dry ingredients to the wet mixture and stir gently until just combined.

Fold in white chocolate chips evenly throughout the batter, spread the batter into the prepared pan.

Crush Biscoff cookies and sprinkle them on top of the batter, pressing gently to stick.

Bake for 30-35 minutes until edges are golden and a toothpick comes out with moist crumbs.

Allow blondies to cool completely in the pan. Optionally, drizzle melted cookie butter on top before cutting into squares.