Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper.

In a large mixing bowl, beat the softened butter until creamy. Gradually add granulated and brown sugars, beating until fluffy.

Mix in the peanut butter until fully incorporated. Add the egg and vanilla extract, blending well.

In another bowl, combine flour, baking soda, baking powder, and salt. Gradually add this mixture into the wet ingredients until just combined.

Fold in the chopped Butterfinger pieces gently.

Chill the dough for at least 15 minutes in the refrigerator.

Scoop generous dough balls onto prepared baking sheets, spaced apart.

Bake for about 10 minutes or until edges are set but centers remain slightly underbaked.

Let cool on pans for a few minutes before transferring to wire racks to cool completely.