Preheat oven to 350°F. Preheat oven to 350F. Butter the bottom and sides of a 9 x13 inch baking pan. Put a long piece of parchment paper in the bottom of the pan, letting the parchment extend up two sides of the pan and overhang slightly on both ends. (This will make it easy to remove the bars from the pan after they have baked.) Butter the parchment.
In a small bowl, whisk together flour, baking powder and salt; set aside.
In the bowl of a stand mixer fitted with the paddle attachment, beat butter and brown sugar until combined, about 1 minute. Beat in eggs and vanilla until smooth.
Stir in flour mixture until just combined, followed by 1 cup of chopped butterfingers.
Spread the batter into the prepared pan. Sprinkle remaining crushed butterfinger bars over top of batter.
Bake 30- 35 minutes, or until the bars are a slightly firm to the touch. Cool completely before cutting into bars.