Red, White & Blue Puppy Chow

Line two baking sheets with parchment. Divide the Rice Chex into three large mixing bowls (about 2 cups per bowl).
In a microwave-safe bowl, combine white chocolate chips, peanut butter, and unsalted butter. Microwave in 30-second intervals, stirring between each, until smooth and glossy (about 60–90 seconds total).
Stir in the vanilla extract until fully incorporated.
Pour about one-third of the warm coating over the first bowl of cereal. Gently fold with a silicone spatula until evenly coated.
Transfer coated cereal to a large zip-top bag with a portion of the powdered sugar. Seal and shake until the cereal looks evenly “snowy.” Spread onto a prepared baking sheet to cool and set.
Repeat coating and sugaring with the remaining two bowls of cereal, dividing the coating and powdered sugar as needed. Let all coated cereal cool completely.
Melt the red and blue candy melts in separate small bowls using short microwave bursts, stirring often. If too thick, thin with a few drops of neutral oil.
Drizzle red melts over one portion of the cooled cereal and blue melts over another. Leave the third portion white for contrast. Allow the drizzles to set fully.
Combine all three colors in a large bowl. Add the red, white, and blue M&Ms and optional sprinkles; toss gently to mix.
Serve right away or store in an airtight container at room temperature for up to 5 days (refrigerate if your kitchen is warm).