Brown-Butter Toffee Blondies

Set the oven rack in the center position. Preheat oven to 350 degrees. Butter one 9×13-inch or two 8-inch square baking pans. Line bottom(s) with parchment paper, leaving an overhang on two sides; butter and flour paper, tapping out excess.

Place the butter into a medium saucepan set over medium heat, As it begins to melt, start swirling the pan frequently and watching the butter carefully. You will notice the butter will crackle, pop and get foamy, and then the milk solids will begin to brown. Once that starts, remove skillet from heat. Smell the butter; it should have a nutty aroma, and be caramel in color.Meanwhile, whisk together flour, baking powder, and salt. Set aside. In the bowl of an electric mixer, combine the cooled brown-butter and both sugars; stir until combined. Attach bowl to mixer; add eggs. Using the paddle attachment, beat on medium-high speed until light and fluffy, about 3 minutes.

Add vanilla, and beat to combine.

Add the flour mixture in three additions, mixing lightly between each addition, followedby all the walnuts and chopped toffee bars.

Mix until just combined, then scrape into prepared pan(s); use a rubber spatula to smooth the batter out evenly.

Bake in the preheated oven until a cake tester inserted in the center comes out clean, 35 to 40 minutes (do not over bake).

Transfer to a wire rack to cool completely before lifting the blondies out with the overhanging parchment. Peel off parchment paper; cut blondies into 18 squares.

Serve warm or at room temperature.