In a heat-safe bowl, add the chocolate chips and melt in the microwave for 30 seconds on 50% power.
Stir and repeat until the chips are completely melted.
Combine the Chex, pretzel sticks, and M&Ms in a large bowl.
Pour the melted white chocolate over the Chex mixture and carefully stir until coated.
Spread the mixture over a long strip of parchment paper and sprinkle with jimmies.
Let it cool and harden for about 1 hour.
Break apart and store in an air-tight container for up to 5 days.
Notes
This recipe will make about 11 cups of Chex mix.
You'll want to work quickly when sprinkling the jimmies on top of the Chex mix because it sets up quickly, and they won't stick to the white chocolate.