In a large microwave-safe bowl, combine the chocolate chips and unsalted butter. Microwave for 30-second intervals, stirring in between, until fully melted and smooth.
Stir in the creamy peanut butter and vanilla extract into the melted chocolate mixture until well-combined.
Add the rice Chex cereal to the bowl and gently fold until all pieces are evenly coated with the chocolate-peanut butter mixture.
In a large resealable plastic bag, add the powdered sugar. Carefully transfer the coated Chex mixture into the bag, seal it tightly, and shake until the cereal is completely covered in powdered sugar.
Pour the mixture back into a large bowl and gently fold in the mini marshmallows and holiday sprinkles for that festive touch.
Spread the puppy chow onto a baking sheet lined with parchment paper to cool and set for about 15-20 minutes.
Notes
Serve in a decorative bowl or individual treat bags tied with colorful ribbons. Sprinkle more holiday sprinkles on top for a cheerful look!