Line a 9×9 baking pan with foil, allowing the foil to hang over the edge for easy removal. Spray the foil with cooking spray.
Place graham crackers on the bottom of the pan, breaking them to fit evenly.
Sprinkle mini marshmallows evenly over the graham crackers.
In a microwave-safe bowl, melt the caramel bits and milk together for 1 minute. Stir and continue heating in 30-second intervals until melted and smooth.
Pour the melted caramel over the marshmallows and gently spread until evenly coated. The marshmallows will melt slightly, which is fine. Make sure to coat evenly so the caramel sticks to the graham crackers.
Sprinkle the chopped Butterfinger Bites on top and press the candies into the caramel/marshmallow mix.
In a microwave-safe bowl, melt the semi-sweet chocolate in 30-second intervals until fully melted.
Drizzle the melted chocolate over the top of the Butterfinger layer.
Chill the bars in the refrigerator for 1 hour or until set.
Once chilled, cut into bars and serve.