Measure 9 cups of Rice Chex cereal into a large heat-resistant mixing bowl and set aside.

In a microwave-safe glass bowl, combine white chocolate chips, creamy peanut butter, and unsalted butter.

Microwave the mixture on high for 60 seconds. Remove and stir with a silicone spatula.

Continue microwaving in 20-second intervals, stirring between each, until the mixture reaches a completely homogenous, fluid state.

Incorporate the vanilla extract and kosher salt into the melted chocolate mixture, stirring until well combined.

Pour the liquid binder over the cereal. Using a large rubber spatula, perform a gentle folding motion to coat all cereal surfaces while minimizing mechanical breakage of the cereal pieces.

Transfer the coated cereal into a 2-gallon resealable plastic bag. Add the powdered sugar to the bag.

Seal the bag with air trapped inside and shake vigorously for 30-45 seconds until the powdered sugar has achieved even coverage on all cereal surfaces.

Spread the Muddy Buddies onto a large baking sheet lined with parchment paper in a single layer to cool and set.

Once the coating has solidified (approximately 15 minutes), toss with Valentine's M&Ms and heart sprinkles. Store in an airtight container at room temperature.