Mix together the cake mix, 1/3 cup butter or margarine and, the egg. Press into the bottom of one 9x13 inch pan and bake at 350 degrees F (175 degrees C) for 12 to 18 minutes. Remove from oven and sprinkle with miniature marshmallows. Return to oven for 1 to 2 minutes or until the marshmallows begin to puff.
In a saucepan over medium heat cook corn syrup, 1/4 cup butter of margarine, vanilla, and peanut butter chips until melted. Remove from heat and stir in the puffed rice cereal and salted peanuts. Spoon mixture over top of marshmallow topped cake and spread to cover. Allow to cool before serving.