Measure the cereal into a large, microwave-safe bowl and set aside. Line a cookie sheet with waxed paper or foil.

In a microwaveable cup, combine brown sugar, butter, and corn syrup. Microwave on high for 1-2 minutes, stirring halfway through, until melted and smooth. Stir in baking soda until dissolved.

Pour the caramel mixture over the cereal and mix to coat evenly. Microwave on high for 3 minutes, stirring every minute. Spread mixture onto the cookie sheet to cool for 10 minutes, then break into pieces.

Once the Chex mix is cool, sprinkle the Reese's minis and marshmallows evenly over it.

Melt the caramel bits with cream in a small bowl, microwaving about 1 minute or until smooth. Drizzle over the mix.

Melt the milk chocolate chips in 20-second intervals, stirring until smooth, and drizzle over the mix. Repeat with the white chocolate chips.

While the drizzle is still wet, sprinkle coarse salt over everything.

Refrigerate until set, then break apart and store in an airtight container.