chewy caramel popcorn and pretzel bars

the goods:

12 cups plain popcorn (from 1/2 cup kernels or 2 microwave packages)

4 cups coarsely chopped small salted pretzels

2 cups sugar

1/2 teaspoon salt

2/3 cup heavy cream

2 cups miniature marshmallows

Coat a 9-by-13-inch baking dish with cooking spray. In a large bowl, toss together popcorn and pretzels. In a medium saucepan, bring sugar, salt, and 1/2 cup water to a boil over medium-high. Boil, undisturbed, until mixture is amber in color, 8 to 12 minutes. Remove pan from heat and slowly pour in cream (mixture will sputter). Immediately add marshmallows; stir until melted.

Pour caramel mixture over popcorn and pretzels and quickly stir with a rubber spatula to coat. Transfer mixture to dish and use a piece of plastic wrap coated with cooking spray to press evenly into dish.

Let cool completely before cutting into bars.