Spray a 9 x 13 inch pan with non stick cooking spray.
Place cereal in a large mixing bowl.
In a large saucepan melt the butter and peanut butter together over medium heat.
Add the marshmallows and stir until melted.
Pour the mixture over the cereal in the big bowl.
Fold in the Butterfinger pieces (reserving 1/2 cup to sprinkle over the top of bars).
Place into the prepared pan and press evenly over the entire pan. Let cool.
Heat the chocolate chips and oil in a glass bowl in the microwave until melted and smooth.
Spoon over the cooled Rice Krispie treats. Sprinkle the remaining Butterfingers over the top.
Let set up for about 20 minutes.
Slice and serve.
Notes
You can modify this recipe by using other types of candy. With chocolate candy, remember it will melt slightly when you add it to the warm marshmallow-cereal mixture. Other candy you can use include the following: Snicker's bars (cut into pieces), Reese's Peanut Butter Cups (cut into pieces), M&M's, Kit Cats (broken into pieces), 100 Grand (roughly chopped), and Twix Bars (cut into pieces).