1/2 cup granulated sugar
3/4 cup corn syrup
1/2 cup firmly packed brown sugar
1/2 cup butter
3/4 cup peanut butter
1/2 tsp vanilla extract
1/2 cup semisweet chocolate chips
1 cup butterscotch chips
Grease a 9 x 12-inch baking pan. Pour Rice Krispies into pan. Set aside.
Bring sugar, corn syrup, brown sugar and butter to a boil in a large saucepan or Dutch oven. Remove from heat and stir in peanut butter and vanilla extract. Pour mixture over the Rice Krispies quickly and stir to mix, patting down evenly.
Frosting: In a small saucepan over low heat, melt semisweet chocolate chips and butterscotch chips. (If desired, skip the butterscotch chips and use 1 1/2 cups melted chocolate chips instead.) Spread melted chips evenly over the top of Rice Krispies bars. Allow to cool before cutting into squares.
Makes about 48 bars.