Preheat oven to 350°F. Line an 8 x 8 baking pan with parchment paper, leaving an overhang on the sides to lift the finished blondies out.
Add butter to a small saucepan and cook over medium heat until brown and bubbly with little bits on the bottom of the pan (approximately 5-6 minutes). Allow to cool.
Mix together flour, baking powder, baking soda, and salt. Set aside.
In a separate bowl, whisk the cooled brown butter, brown sugar, and vanilla together until combined. Add egg and mix well. Slowly add in the dry ingredients and stir together until just combined. Fold in the chopped candy bars. The batter will be very thick. Spread evenly into prepared baking pan and top with additional candy, if desired.
Bake for 20 minutes or until lightly browned on top. Remove from the oven and allow to cool completely before cutting into squares. Enjoy!
