01 -
Place the Rice Chex in a very large mixing bowl. Line a sheet pan with parchment paper and keep it nearby for cooling.
02 -
In a large microwave-safe bowl, combine the white chocolate chips, sweetened condensed milk, and butter. Microwave in 20-30 second bursts, stirring after each, until smooth.
03 -
Stir in the dry pistachio pudding mix, vanilla extract, and salt until the coating is evenly green and glossy.
04 -
Pour the warm pistachio coating over the cereal. Fold gently with a wide spatula until the cereal is evenly coated, taking care not to crush it.
05 -
Sprinkle in half of the powdered sugar and toss gently. Add the remaining powdered sugar and toss again until the pieces look pale and dry on the outside.
06 -
Spread the puppy chow in a single layer on the prepared pan. Sprinkle with chopped pistachios if using, then cool for 30 minutes before serving or storing.