Preheat the oven to 375° F. Combine flour, baking soda, and salt in a small bowl and set aside. With an electric mixer, beat sugar and butter until creamy. Beat in the eggs and vanilla until just combined. Gradually beat in the flour mixture. Fold in Butterfinger® pieces by hand. Drop by slightly rounded tablespoonfuls onto an ungreased baking sheet. Bake for 10-12 minutes or until lightly browned.