Prepare a 9"x13" baking pan by spraying lightly with non-stick cooking spray, and set aside.
Get two very large bowls. Into one bowl, add the rice cereal, and set aside.
Into the other bowl, add mini marshmallows and butter. Microwave for 2-4 minutes, or until the marshmallows are very soft and puffy.
While the marshmallows melt, measure out the 1/3 cup peanut butter and set aside.
Carefully remove the bowl of marshmallows from the microwave and stir until the (now melted) butter is incorporated.
Working quickly, add 1/3 cup peanut butter to melted marshmallows and stir.
Pour the peanut butter/marshmallow mixture over the bowl of rice cereal and use a rubber spatula (sprayed with non-stick spray) to quickly stir and combine the ingredients.
As soon as the cereal has been coated with the mixture, pour/scoop the rice krispies mixture into the prepared pan.
Use the spatula to press the mixture into the pan and flatten and even out as needed. Set aside to cool.
While the treats cool, in a small saucepan add caramel bits and milk.
Heat over medium heat until melted, stirring as needed.
Pour melted caramel over rice krispie treats, as evenly as possible.
In a small bowl, add chocolate chips and melt at 50% power in the microwave until almost melted (in 30 second intervals). Stir until melted and smooth.
Pour chocolate over caramel layer, using an offset spatula to spread, as needed.
Allow to cool about 30 minutes before cutting.
Store treats covered and in a cool place (on the counter) up to two days.