How to Make It
Melt butter in a large saucepan over medium, and cook, stirring occasionally, until browned, about 3 minutes. Stir in marshmallow creme and cashew butter. Cook, stirring often, 2 minutes. Remove from heat; stir in cereal until evenly coated.
Coat a 13- x 9-inch baking dish with cooking spray. Press cereal mixture into baking dish; top with milk chocolate pieces, pressing to adhere.
Bring 2 inches of water to a boil in a medium saucepan over medium-high. Place a heatproof bowl on top of saucepan. (Water shouldn’t touch bottom of bowl.) Add bittersweet chocolate to the bowl; cook, stirring occasionally, 1 minute or until chocolate is melted. Drizzle over cereal mixture.
Wipe bowl clean. Add butterscotch chips to bowl; return to top of saucepan. Reduce heat to low, and cook, stirring often, 4 minutes or until melted. Add milk; whisk until smooth. Drizzle over cereal mixture. Chill, uncovered, 20 minutes. Slice into 16 squares.