Butter a 9x13 baking dish with 1 tablespoon of the salted butter. Set aside.
In a large sauce pot on medium-low heat, melt the remaining 4 tablespoons of salted butter, peanut butter, and marshmallows. Stir often to avoid burning the melted marshmallows. This will take about 3 to 5 minutes.
Remove the large pot from the heat and stir the vanilla extract and rice Krispie cereal into the melted marshmallow mixture.
Stir to incorporate all the ingredients evenly.
Spread the peanut butter Rice Krispie mixture into the prepared dish and gently press it into an even layer. Do not pack the mixture into the dish too tightly. This will ensure that your rice Krispie treats are light and chewy.
In a microwave-safe bowl, melt the milk chocolate chips for 1 minute at 50% power, stir and heat in additional 30-second increments until completely melted. Stir the melted chocolate until completely smooth. Be sure not to overheat the milk chocolate chips, or they will seize up and be unusable.
Spread the melted chocolate evenly over the dish of peanut butter rice Krispies.
Allow the peanut butter Rice Krispie treats to chill for 30 minutes, or up to an hour, to allow the chocolate to firm up before slicing and serving.
You can cut this recipe in half and make them in an 8x8 square pan if this recipe makes too many. That is never the issue in my house, so I often will double the recipe. These keep great in the refrigerator and, when packed in your child’s lunch, will be perfectly chewy and delicious by the time they get to eat them.
You can spray your hands, spatula, or wooden spoon with a little bit of cooking spray so that the gooey mixture doesn’t stick when you are mixing it.
When melting your chocolate chips, be very careful not to overheat them in the microwave. If your microwave has a “melt” preset, then you can use that according to your microwave's manual. You can also melt them on the stovetop in a small saucepan on medium-low heat or in a double boiler. Use the method that works best for you.
Once the chocolate layer has firmed up, you can slice your peanut butter Rice Krispies into single servings and store them in a lidded rectangular container. I would suggest you place a piece of parchment paper between the layers of Rice Krispie treats to avoid them from sticking to each other.