- 1 (16 ounce) jar salted peanuts, divided
- 1 (10 ounce) package peanut butter chips (such as Reese's®)
- 3 tablespoons butter
- 1 (14 ounce) can sweetened condensed milk
- 2 1/2 cups marshmallows
- Pour 1/2 of the peanuts into the bottom of a 9×13-inch baking dish.
- Melt peanut butter chips and butter in a microwave-safe glass or ceramic bowl in 30-second intervals, stirring after each melting, for 1 to 3 minutes. Stir in sweetened condensed milk and microwave until heated through, about 30 seconds more.
- Stir marshmallows into butter mixture until completely incorporated and melted. Pour marshmallow mixture over peanuts into the baking dish. Sprinkle remaining peanuts over the top, cover the peanuts with a sheet of waxed paper, and press down to fill the pan and create an even layer. Remove wax paper and cool completely before cutting into squares.