Start by greasing a 9x13-inch baking dish with cooking spray or line it with parchment paper for easy removal later.

Unwrap the Butterfinger bars and place them in a ziplock bag. Crush the bars into small pieces, keeping some larger chunks.

In a large non-stick pot over medium heat, melt the unsalted butter completely. Add the mini marshmallows and stir until fully melted and smooth.

Remove the pot from heat and mix in the creamy peanut butter, stirring until completely incorporated.

Pour in the crushed Butterfinger candy bars and carefully stir to combine.

Gently fold in the Rice Krispies cereal using a spatula; ensure all cereal is coated with the gooey mixture.

Pour the entire mixture into the prepared baking dish and spread evenly with a greased rubber spatula.

Allow the Butterfinger Rice Krispies Treats to cool completely at room temperature for about 1 hour.