Chocolate Candy Chex Mix

From Lisa Bearnson's website.

8 C. Chocolate Chex cereal
3/4 C. packed brown sugar
6 Tbsp. butter
3 Tbsp. light corn syrup
1/4 tsp. baking soda
1 C. MINI Reese’s Peanut Butter Cups
1 C. mini marshmallows
1/2 C. caramel bits
1 Tbsp. heavy cream
1/2 C. milk chocolate chips
1/2 C. white chocolate chips
1 tsp. coarse sea salt, optional

Pour measured cereal into a large microwaveable bowl. Line cookie sheet with waxed paper. In 2-cup microwaveable measuring cup, microwave brown sugar, butter, and corn syrup uncovered on high for 1-2 minutes, stirring after 1 minute, until melted and smooth. Stir in baking soda until dissolved. Pour caramel mixture over cereal, stirring until evenly coated. Microwave on high for 3 minutes, stirring every minute. Spread on cookie sheet. Cool 10 minutes. Break into bite-sized pieces. Make sure Chex mixture is cool to the touch (so candy doesn’t melt). Evenly sprinkle mini peanut butter cups and mini marshmallows over the Chex mixture. In a small microwaveable bowl, microwave caramel baking bits and cream uncovered on high for 1 minute or until chips can be stirred smooth. Use a spoon or fork to drizzle over Chex mixture. Repeat with milk chocolate chips and again with the white chocolate chips. If desired, quickly sprinkle coarse sea salt over all the Chex mixture while candy drizzles are still wet. Refrigerate until set. Break apart and store in tightly covered container.