Place the Corn Chex cereal in a large mixing bowl.
In a microwave-safe bowl, combine the white chocolate chips, peanut butter, and butter.
Microwave in 30-second intervals, stirring between each, until smooth.
Stir in the vanilla.
Pour the melted mixture over the cereal and gently stir until evenly coated.
Place the powdered sugar in a large zip-top bag.
Add the coated cereal and shake until completely coated.
Spread the muddy buddies onto a baking sheet.
While still slightly tacky, add the Valentine's M&Ms, mini pretzel knots, and heart-shaped sprinkles. Toss gently to combine.
Allow to set for about 20 minutes.
Break apart and serve or store in an airtight container.