Line a large baking sheet or countertop area with parchment paper to give you a spot to spread the coated cereal out to cool later.

Set out a large mixing bowl for the cereal and a separate microwave safe bowl for the chocolate mixture.

Measure 6 cups of Rice Chex cereal and 2 cups of the Golden Grahams cereal into the large mixing bowl. Set aside the remaining 1 cup of Golden Grahams for later.

Measure 1 cup of the mini marshmallows and set the remaining 1/2 cup aside for the topping.

In the microwave safe bowl, combine the semisweet chocolate chips, peanut butter, and unsalted butter.

Microwave on high for 1 minute, then remove and stir well. If not fully smooth, return to the microwave in 15 to 20 second bursts, stirring after each one, until completely melted and glossy.

Stir in the vanilla extract once the mixture is smooth.

Pour the melted chocolate mixture over the Rice Chex and Golden Grahams in the large mixing bowl.

Using a rubber spatula, gently fold the cereal until every piece is evenly coated in chocolate, working slowly so the cereal does not crumble.

Fold in the 1 cup of reserved mini marshmallows, stirring just until they are lightly coated and distributed through the mixture.

Transfer the coated cereal into a large gallon size resealable storage bag.

Add the powdered sugar to the bag, seal it tightly, and press out as much air as possible.

Shake the bag vigorously until every piece of cereal is fully coated in a smooth, even layer of powdered sugar.

Pour the coated cereal onto the parchment paper lined baking sheet in a single layer.

Let it sit undisturbed for 10 to 15 minutes, or until the chocolate coating has firmed up and is no longer tacky to the touch.

Once cooled, transfer the mixture to a large serving bowl.

Add the remaining 1 cup of Golden Grahams cereal directly into the bowl with the cooled puppy chow.

Sprinkle in the remaining 1/2 cup of mini marshmallows, then scatter the broken graham cracker pieces and chocolate candy bar chunks over the top.

Gently toss everything together with a spatula or clean hands until the toppings are evenly distributed throughout the mix.