Pour 1 cup of the peanuts into the baking dish. Spread around to cover the bottom.
Melt 2 Tablespoons butter and 10 ounces peanut butter chips in a medium pan over medium-low heat until smooth and creamy. Add 3/4 can sweetened condensed milk and 2 cups mini marshmallows. Stir until all mixed.
Pour over peanuts in baking dish.
Top with remaining peanuts and let cool. Refrigerate until firm before slicing.
Notes
Storage: Store in an air tight container in the fridge.