Prep. Line a baking sheet with parchment paper and set aside. Set out another piece of parchment paper (on the counter or on another baking sheet). Place the powdered sugar in a gallon sized zip-top bag and set aside.
Make the puppy chow. Place the Chex cereal into a large mixing bowl and set aside.
Place your semi-sweet chocolate chips and peanut butter in a microwave-safe bowl and microwave in 30-second increments, stirring after each cycle, until the chocolate is completely melted and smooth.
Pour the melted chocolate and peanut butter mixture over the Chex.
Gently stir until all of the ingredients are well coated. Then let the chocolate-peanut butter coated cereal rest for a few minutes.*
Transfer the coated cereal into the resealable plastic bag with the powdered sugar in it.
Close the bag and shake to coat the cereal with the powdered sugar. You'll need to tip the back sideways and upside down throughout shaking to distribute the powdered sugar.(I recommend peaking into the bag periodically and adding more powdered sugar in ¼ Cup increments if you're noticing there are sections of cereal that are still wet / without powdered sugar coating it).
Pour the coated cereal onto a lined cookie sheet, spreading it to the edges to dry.
Video
Notes
*Tip for best results: be sure to fully coat your cereal with the melted chocolate and peanut butter mixture - no plain cereal should be showing! Take an extra minute or two to continue stirring the melted chocolate and peanut butter mixture together with the cereal to ensure all of the cereal is well coated (you don't want to see any bare cereal). This allows the powdered sugar to coat all parts of your cereal, resulting in the very best puppy chow.*Tip for best results:to create optimal clusters, and limit the amount of powdered sugar used, let the coated cereal rest a few minutes before transferring it to the zip-top bag to shake and coat again. This helps you create some 'clumps' of cereal which area always a delight to bite into, and also helps ensure you don't have an overly sweet treat due to needing extra powdered sugar to coat all the pieces. If the chocolate coating is too wet / warm, the powdered sugar tends to soak up into the chocolate instead of creating a nice coating as desired.Store puppy chow in an airtight container or zip top bag for up to 1 week at room temperature or up to 2 weeks in the refrigerator. You can also freeze this treat for up to 2 months if desired.Variation Ideas:
Swap out some or all of the Rice Chex. Some people like to use a blend of Rice Chex and Corn Chex (just use equal portions of each) for puppy chow. Crispix is another great alternative to the Rice Chex (replace the Rice Chex completely).