Line a baking sheet with aluminum foil. Set aside.
In a large Ziploc bag, add powdered sugar. Set aside.
In a large skillet or pot over low heat, add 1 cup chocolate chips and ½ cup peanut butter. Stir constantly to melt and prevent burning. Once melted, add ¾ cup marshmallows. When the marshmallow starts to melt, add 6 cups of cereal and stir gently with a spatula until well coated.
Transfer the cereal into the prepared Ziploc bag. Seal and shake to coat with powdered sugar. It’s ok to have a few clusters. You can break apart some through the bag. Carefully pour everything into the prepared baking sheet. Allow to cool completely.
If serve right away or same day, add the optional mix (½ cup marshmallows, 1/3 cup chocolate chips, & 1/3 cup cereal) to the puppy chow. If not, store in an airtight container. Add the mix when ready to serve.