Mix marshmallows and peanuts in a large bowl. Set aside.
Melt chocolate chips, sweetened condensed milk, and butter over low heat.
Stir until melted and pour over marshmallows and peanuts.
Mix until evenly coated.
Pour into wax paper lined 13 x 9 inch pan.
Chill at least two hours.
Peel off wax paper and cut into pieces.