Line a 9x13-inch baking dish with parchment paper.
In a large saucepan over medium heat, melt the chocolate chips and butter.
Stir in the sweetened condensed milk until smooth and well combined.
Remove from heat and fold in the marshmallows and peanuts.
Pour the mixture into the prepared baking dish and spread evenly.
Refrigerate for at least 2 hours or until set.
Cut into squares and enjoy!