Preheat oven to 350 degrees.

In a large bowl, combine the peanuts and Rice Krispies. Set aside.

In a medium bowl, mix the cake mix, egg and 1/4 cup of melted butter.

Press the mixture into a lightly greased 9×13 pan. Bake for 10-12 minutes.

Sprinkle the marshmallows evenly over the hot crust. Return to oven for 3-4 minutes, or until the marshmallows are puffy and just beginning to turn golden.

In a medium saucepan over medium heat, combine the peanut butter chips, corn syrup and the remaining butter.

Heat and stir until peanut butter chips are melted and the mixture is smooth. Stir in vanilla.

Pour the peanut butter mixture over the peanuts and Rice Krispies and stir to coat well.

Carefully spread the peanut mixture over the marshmallows. Refrigerate until set.