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