Preheat oven to 350 degrees F.
Spray 9x13" baking dish with non-stick cooking spray and set aside.
In large bowl with electric mixer, beat together butter and sugars.
Add eggs, one at a time, until completely combined.
Add vanilla.
In medium bowl, combine flour, baking soda, and salt.
Slowly add flour mixture to butter mixture, mixing on low speed until combined.
Fold in Butterfinger bars and chocolate chips.
Spread batter into prepared pan. It will be very thick so you can use your hands or a spatula to spread it out.
Bake in preheated oven 25 minutes, until golden brown. They will still be a little gooey in the middle but will set up once cooled.
Cool completely then cut into bars.
Enjoy!