Line a 9 x 9 inch pan with parchment or foil.
In a medium-sized pot over low heat, melt together the chocolate chips and peanut butter, mixing until smooth.
Stir in walnuts and peanuts and remove from heat. Allow to cool for 3-4 minutes.* Fold in the marshmallows until coated.
Spread mixture into the lined pan and refrigerate for 2 hours or until firm.
Cut into 16 squares and serve.
