Preheat the oven to 350°F. Prepare an 8”x 8” square metal pan with parchment paper. Leave excess hanging over the sides of the pan for easy removal after baking.
Melt the butter in a saucepan over medium low heat until it turns golden brown with a nutty smell (5-7 minutes), stirring frequently. It may foam up slightly. Keep stirring and checking the color. Once it starts to brown, it will turn quickly so remove from heat as soon as it starts to darken. Set aside to cool for 5 minutes.
Combine the butter and brown sugar in a large mixing bowl. Beat in the eggs and the vanilla extract, scraping down the sides of the bowl as needed. Continue to mix on medium high speed for 2-3 minutes until the mixture light, airy, and pale in color.
Mix in the cookie butter, scraping down the bowl as needed. Add in the flour, baking powder, and salt. Mix just until the dry ingredients are incorporated without overmixing. The texture will be between a batter and a dough.
Pour the batter into the pan and smooth it with a rubber spatula. Bake for 22-25 minutes until the edges are lightly golden brown and the center is almost fully set.
Let the blondies cool in the pan for 5-10 minutes. Remove from the pan, cut into squares and serve!
Notes
You can substitute the brown butter with the same amount melted butter if desired. This will make the flavor of the blondies a little less rich.
Speculoos cookie butter can be used in place of Biscoff if needed.
Use room temperature ingredients (except the butter).
Use a metal pan for this blondie recipe. Using a glass pan may alter the outcome.
Store in a sealed bag or container for up to 4 days. Freeze for longer storage,
Try this recipe with mix-ins like chopped nuts, chocolate chips, or toffee bits.