Place the brownie mix in a microwave-safe bowl and heat in 30-second increments, stirring well between each heating, for 3-5 minutes or until the mixture reaches 165℉. Set the heat-treated brownie mix to the side.
2 cups brownie mix
In a second, large microwave-safe bowl, combine the chocolate chips, peanut butter, and salted butter and heat for 60 seconds.
1¼ cup dark chocolate chips, ⅓ cup creamy peanut butter, 3 tablespoons salted butter
Stir the mixture well and continue heating in 15-second increments, if needed, until smooth and completely melted. Add in the vanilla and stir well.
1 teaspoon pure vanilla extract
Gently fold in the Rice Chex cereal, until completely coated with chocolate. Be careful not to crush the cereal pieces.
7 cups Rice Chex cereal
Place ⅓ of the brownie mix in a large resealable plastic bag.
Add the Chex mixture.
Pour the remaining brownie mix on top of the Chex cereal and seal the bag.
Shake the bag well, until the Chex mixture is completely coated with brownie mix.
Spread the puppy chow on a large baking sheet lined with aluminum foil or parchment paper, and let it cool completely before serving.