Spray an 8 x 8" baking dish with cooking spray and set aside.

In a large bowl, add the Rice Krispies cereal and the peanut butter chips (if using). Set this aside too.

In a 2 quart saucepan, melt the butter, marshmallows and peanut butter over medium low heat. Stir constantly until all the ingredients are melted completely and smooth.

Once melted, turn off the burner, and immediately pour the peanut butter marshmallow mixture over the cereal. 

Using a rubber spatula, quickly mix and combine all the ingredients until the cereal is well coated and there is no remaining marshmallow mixture pooling at the bottom of the bowl.

Dump the peanut butter Rice Krispie mixture into your prepared baking dish.

Use a piece of plastic wrap to press the cereal mixture into the dish tightly and evenly. 

Set aside while you prepare the chocolate peanut butter topping.

To make the topping, place the chocolate chips and 1/4 cup of peanut butter into a heat safe bowl. You can melt the chocolate and peanut butter by microwaving in 30 second increments or you can set the bowl over a pan of barely simmering water. Stir and heat the mixture until it's completely melted and smooth.

Pour the chocolate mixture over the top of the Peanut Butter Rice Krispie Treats. Use an offset spatula or a spoon to smooth the chocolate into an even layer.

Allow the mixture to set. You can pop the pan in the fridge for about 1-2 hours or let it sit at room temp for several hours.

Once the treats have cooled and set completely, run a knife along the edge of the pan and cut the treats into 12 bars.

Store treats in an airtight container at room temperature for 3-4 days.