In a mixing bowl, combine cake mix, vegetable oil, and eggs with an electric mixer. Stir in one cup of crushed Butterfinger.
Pour batter into prepared pan and bake 20 minutes or until a toothpick inserted in the middle comes out clean.
While the bars are cooling, prepare your frosting. In a mixing bowl, combine butter and powdered sugar with a splash of milk. Add more sugar if it’s too thin or more milk if it’s too thick. Once your frosting reaches the desired consistency, stir in the remaining 2 cups of Butterfinger candy. Top cooled bars with Butterfinger frosting.
Refrigerate bars at least 2 hours before slicing and serving.
The whole time I made these bars, I kept thinking about how years ago Bart Simpson was the Butterfinger spokesperson and he would always say…”nobody better lay a finger on my Butterfinger”. This is how I felt about these bars…they’re so stinkin’ good that I didn’t want anyone laying a finger on them :).