Use softened butter to lightly butter the bottom and sides of an 8x8-inch pan. Set aside.
On the stove top in a heavy bottomed pan melt together the sweetened condensed milk and peanut butter. Cook over medium-low for around 8-10 minutes until heated through and bubbling gently. Stir constantly to avoid sticking.
Remove from the heat adding the vanilla extract and the peanut butter chips. Stir until the chips are completely melted.
Mix-in the chopped Nutter Butter cookies and marshmallows. Stir until evenly distributed. Some marshmallows should remain whole.
Working quickly spread into the prepared pan. Sprinkle the top with chopped peanuts.
Chill 2 hours or until set, then cut into desired sized pieces. Store chilled.