• Nonstick vegetable oil spray
• ½cup (1 stick) unsalted butter
• 1tsp. black mustard seeds
• 1 tsp. cumin seeds
• 1½ tsp. Diamond Crystal or 1 tsp. Morton kosher salt
• 1 tsp. Urfa biber or other mild pepper flakes
• ½ tsp. cayenne pepper
• 3 cups large marshmallows (about 5 oz.)
• 8 cups unsalted popped popcorn

Line an 8x8" baking dish with overlapping pieces of parchment paper, leaving overhang on all sides. Lightly coat parchment with nonstick vegetable oil spray.Melt ½ cup (1 stick) unsalted butter in a large pot over medium heat. Add 1 tsp. black mustard seeds and 1 tsp. cumin seeds and cook, stirring often, until butter is foaming and beginning to brown and seeds are beginning to pop, about 4 minutes. Add 1½ tsp. Diamond Crystal or 1 tsp. Morton kosher salt, 1 tsp. Urfa biber or other mild pepper flakes, and ½ tsp. cayenne pepper, followed by 3 cups large marshmallows (about 5 oz.), and cook, stirring, until marshmallows are mostly melted, about 2 minutes. Remove from heat and stir until marshmallows are fully melted.Using a rubber spatula, gently fold 8 cups unsalted popped popcorn into marshmallow mixture until evenly combined.Scrape mixture into prepared pan, press into corners, and smooth surface. Let cool in pan at least 15 minutes. Lift out of pan using parchment; cut into bars.