In a large mixing bowl, thoroughly combine the Rice Chex and Corn Chex cereals. Set aside to prepare for coating.
In a medium saucepan, over low heat, melt the unsalted butter, semi-sweet chocolate chips, and creamy peanut butter together. Stir frequently to ensure the mixture becomes smooth and homogenous.
Once melted, remove the saucepan from heat and stir in the vanilla extract along with a pinch of sea salt to enhance the flavors.
Carefully pour the melted chocolate and peanut butter mixture over the combined cereals in the large bowl. Using a spatula, gently fold the cereals until they are well coated, making sure to cover every piece evenly.
After the cereals are coated, add in the mini pretzels and holiday-themed M&M's. Toss gently to ensure everything is evenly distributed throughout the mix.
In a large resealable plastic bag, add the powdered sugar. Slowly pour the coated cereal mixture into the bag. Seal the bag tightly and shake gently until the mix is thoroughly coated with powdered sugar.
Spread the sugar-coated mix out evenly onto a large baking sheet lined with parchment paper, allowing it to cool and set.
Once cooled, you can store your Holiday Puppy Chow Chex Mix in an airtight container or serve it immediately for a festive treat!
Notes
Serve in festive bowls or package in cellophane bags for gifts.