Add the creamy peanut butter, chocolate chips, butter, and extract to a medium-sized, microwave-safe bowl.
Microwave in 30-second intervals until creamy. If for some reason, your chocolate gets a little thick, add in additional butter.
Add 9 cups of Chex mix to a jumbo mixing bowl.
Once your mixture is creamy, pour it over the 9 cups of Chex Mix cereal.
Mix cereal and chocolate mixture with your spoon gently enough to coat each piece with the chocolate peanut butter mixture.
Once the cereal is fully coated, add 2 cups of powdered sugar to a large 1 gallon zippered bag and shake half of the coated cereal. You will need to do this in 2 separate batches.
After all the pieces are coated with powdered sugar, they will have a white appearance. Spread them on the baking sheet.
Add the white chocolate morsels, marshmallows, Sixlets, and snack mix.
Stir to mix and store in in air-tight container, or bag for gifting.
This is best kept in a dry place without humidity which can make the mix feel wet. Personally, I find this mix is best enjoyed within 3-5 days of creating when stored perfectly.