Salted Nut Roll Bars

Preheat the oven to 350°F. Place a rack in the middle of the oven. Make a foil sling for a 9 x 13-inch metal baking pan. Lay 2 sheets of foil in the pan perpendicular to each other, with extra foil hanging over the edges of the pan. Push the foil into the corners and up the sides of the pan. Grease the foil with cooking spray.

Make the crust: In a medium bowl, stir together the cake mix, melted butter, and egg until combined. Using greased hands, press the mixture evenly into the bottom of the prepared pan and bake until golden brown, 10 to 12 minutes.

Melt the marshmallows: Sprinkle the marshmallows evenly over the warm crust and bake until melted, about 3 minutes.

Make the topping: While the marshmallows melt, in a large saucepan melt the butterscotch chips, corn syrup, and the remaining 4 tablespoons of cold butter over medium heat until the chips are completely melted, 5 to 7 minutes. Stir the mixture frequently as it melts. Remove from the heat. Gently stir in the peanuts and cereal until fully coated with the butterscotch mixture.

Assemble the bars: While the crust and marshmallows are still warm, dollop the cereal mixture over the melted marshmallows in an even layer. Let the bars sit at room temperature until set, about 1 hour and 30 minutes.

Cut and serve: Using the foil overhang, lift the bars out of the pan and transfer to a cutting board. Cut into 24 pieces. Serve. Store the bars in an airtight container at room temperature for up to 3 days.