Preheat oven to 350°F. Grease and flour a 13x9-inch baking pan.
In a small bowl, whisk together flour, baking powder and salt; set aside.
In a medium bowl, with electric mixer at medium speed, combine butter and brown sugar.
Beat in eggs and vanilla until smooth.
Stir in flour mixture and 1 cup of crushed butterfingers.
Spread in prepared pan. Sprinkle remaining crushed Butterfinger bars over top of batter.
Bake 30- 35 minutes, or until the bars are a bit firm to the touch. Cool completely before cutting into bars.