Spray a 13 x 9 pan with oil. Microwave (or heat in a small pan) the peanut butter chips and butter, stirring till blended. Add cereal and stir to mix.

Spread cereal mixture into prepared pan, pressing into an even layer. Melt chocolate chips. Add corn syrup and stir to blend. Spread over cereal mixture in pan. Sprinkle chopped nuts on top. Refrigerate until firm.