Step 1

Melt butter in a large saucepan over medium. Remove and reserve 1 cup marshmallows; add remaining marshmallows to saucepan. Cook, stirring often, until just melted. Remove from heat and fold in popcorn, pretzels, ¾ cup chopped peanuts, and remaining 1 cup marshmallows.

Step 2

Coat a 13- by- 9-inch baking dish with cooking spray. Press mixture into prepared pan and sprinkle with remaining ¼ cup peanuts. Let set until firm, about 30 minutes. Cut into 3- x 3¼-inch bars and serve.