Place butter and peanut butter chips in a large saucepan and melt them over medium heat until you achieve a smooth consistency.
Add condensed milk, vanilla extract and marshmallows to the melted butter-peanut butter mix. Stir until the mix is smooth and fully incorporated.
Grease a 9×13-inch rectangular baking dish with butter or non-stick spray. Spread half of the peanuts across the baking dish.
Pour the mix from step 2 evenly over the peanuts, and then sprinkle the remaining peanuts on top.
Refrigerate or let sit at room temperature until it sets. Cut candy into serving bars and enjoy.
