Use 1 tsp of butter to grease a 9" x 9" pan. Then melt the remaining butter in a large pot over low heat. Fully coat the sides of the pot with the butter, then add the marshmallows to the pot. Stir the marshmallows until fully melted.
Add the chex cereal and stir until it's mixed through. Stir in the crushed peanuts and peanut butter chips. Mix thoroughly, until mixed through. Pour the cereal mixture into the prepared pan. Use wet fingers to press the cereal bars down flat.
Drizzle the peanut butter over the bars then sprinkle the salt on top. Refrigerate for 2 hours or overnight.
This recipe makes 12 Peanut Butter Cereal Bars.