Pour chex cereal into a large microwavable bowl. Set aside.
In a separate microwavable bowl, microwave brown sugar, butter, and corn syrup for 1 minute. Stir until smooth. (Microwave for another 30 seconds if needed)
Stir in baking soda.
Pour caramel mixture over the cereal and stir to evenly coat.
Microwave cereal mixture for 2 minutes, stirring after every minute.
Spread onto a cookie sheet lined with waxed or parchment paper. Allow to sit for about 10 minutes.
Break into pieces.
Evenly sprinkle peanut butter cups and marshmallows over the top of the cereal.
In a small microwavable bowl, add caramel bits and cream. Microwave for 1 minute, or until it can be stirred smooth.
Use a spoon to drizzle caramel evenly over the top of the cereal.
Microwave milk chocolate in 30 second increments, stirring after each, until smooth. (Mine takes 1 to 1.5 minutes)
Using a spoon drizzle the chocolate over the cereal mixture.
Microwave white chocolate in 30 second increments, stirring after each, until smooth. (Mine takes 1.5 minutes)
Using a spoon drizzle the white chocolate over the cereal mixture.
Sprinkle coarse sea salt over the top while the caramel, and chocolates are still wet.
Allow chocolate to set until hardened. (Place in the fridge for a quicker set)
Break apart and store in airtight container.