1Heat oven to 350°F (325°F for dark or nonstick pan). In large bowl, beat cake mix, butter and egg with electric mixer on low speed until crumbly. Press in ungreased 15x10x1-inch pan using plastic wrap. Bake 10 to 12 minutes or until light golden brown. Sprinkle with marshmallows. Bake 3 to 5 minutes or until marshmallows puff.
2In large microwavable bowl, microwave butterscotch and chocolate chips uncovered on Medium-High (70%) 1 minute; stir. Microwave 1 to 2 minutes longer, stirring every 30 seconds, until mixture can be stirred smooth. Stir in cereal and peanuts.
3Immediately spoon cereal mixture over hot marshmallow layer. Let stand about 1 hour or until cool and set. For bars, cut into 10 rows by 6 rows. Store loosely covered.