Chicago mix popcorn is that deliciously addictive combination of caramel popcorn and cheddar popcorn. They say it was created when customers of Garrett Popcorn Shops in Chicago started mixing individual bags of caramel and cheddar popcorn together, so the Garretts started doing it for them.  Chicago mix popcorn was actually the inspiration behind these bars. I took each flavor profile —- sweet and salty — then ran with it and added even more of each. So I wandered down the chip aisle and grabbed pretzels, Fritos, and honey roasted peanuts. Then down the sweet side of the store came the white and dark chocolate and M&Ms. Not only for sweetness, but to add some color. The peanut butter in the marshmallow mixture was brought in to tamp down the sweetness. Same with the sea salt.