Scotcheroos: Chocolate & butterscotch on peanut butter cookie bars (1965)

Instructions

1. Combine sugar and corn syrup in a 3-quart saucepan.
2. Cook over moderate heat, stirring frequently, until sugar dissolves and mixture begins to bubble. 
3. Remove from heat.
4. Stir in peanut butter.
5. Mix well.
6. Add Rice Krispies cereal.
7. Stir until well-coated.
8. Press mixture into buttered 13- by 9-inch pan.
9. Melt chocolate and butterscotch morsels together over very low heat or over hot but not boiling water, stirring until well-blended.
10. Remove from heat; Spread evenly over Rice Krispies mixture.
11. Cool stand until firm.