1Heat oven to 350°F (325°F for dark or nonstick pan). Grease bottom only of 13x9-inch pan with shortening or cooking spray. Make brownies as directed on box. Immediately after removing from oven, sprinkle with marshmallows. Bake 1 to 2 minutes longer or until marshmallows just begin to puff.
2In 3-quart saucepan, heat corn syrup, butter, vanilla and peanut butter chips over medium heat 3 to 4 minutes, stirring constantly, until chips are melted. Remove from heat; stir in cereal and peanuts. Spread evenly over marshmallows. Refrigerate about 45 minutes or until firm. For brownies, cut into 9 rows by 4 rows. Store in refrigerator.