Place cornflakes in a resealable plastic bag. Crush with rolling pin or hands until fine; set aside. Line 13 x 9-inch pan with foil; spray with cooking spray.
Combine sugar, corn syrup and peanut butter in a large saucepan over medium heat. Heat mixture, stirring constantly, just until bubbles form around the edges. Remove from heat and stir in butterscotch chips until melted. Add crushed cornflakes and mix well.
Spread into prepared pan, pressing into corners. Immediately sprinkle milk chocolate chips evenly over the top. Set aside for 5 to 10 minutes until chips have melted. Evenly spread chocolate over the peanut butter layer.
Refrigerate 30 to 60 minutes to set the chocolate. Lift foil out of pan and cut into bars.