Martha makes sweet and spicy popcorn crunch.
Preheat oven to 250 degrees. Line 2 baking sheets with nonstick baking mats; set aside.
In a large heavy-bottomed pot, heat oil over medium heat. Add 3 popcorn kernels and cover until they pop. Add remaining popcorn kernels, cover, and shake pot continuously over burner until popcorn is completely popped, 3 to 5 minutes. Transfer popcorn to large bowl; add peanuts and set aside.
Combine butter, sugar, and corn syrup in a medium pot over medium heat. Cook, stirring occasionally until sugar has dissolved. Increase heat to medium-high, and cook, without stirring, until golden brown, about 5 minutes, swirling pot occasionally.
Remove mixture from heat and quickly stir in salt and cayenne with a heatproof spatula or spoon. Immediately pour over popcorn mixture and stir to incorporate. Divide popcorn mixture evenly between baking sheets. Transfer to oven and bake, about 30 minutes, stirring occasionally.
Let cool on sheet pans before breaking apart into clusters. Store popcorn in an airtight container for up to 1 week.