Preheat oven to 350°F (177°C).

Combine flour, baking soda, and salt in small bowl and set aside. With an electric mixer, beat sugar and butter until creamy. Beat in egg until just combined.

Gradually beat in flour mixture. Stir in butterfinger pieces by hand. The dough will be very thick. Drop by slightly rounded tablespoonfuls onto ungreased baking sheet.

Bake for 10-12 minutes or until lightly browned. Allow to cool on the baking sheets for 5 minutes, then transfer to a wire rack to cool completely.