10 cups of freshly-popped popcorn (or 3.5-oz bag of microwave popcorn, plain)
1 cup light brown sugar
¼ cup light corn syrup
6 tablespoons unsalted butter, melted
2 tablespoons water
¼ teaspoon salt
2 teaspoons vanilla extract
½ teaspoon baking soda
1 cup lightly salted peanuts
1. Preheat oven to 250 degrees F. Line a rimmed baking sheet with parchment paper; set aside.
2. Pop the popcorn. Coat a large mixing bowl with nonstick cooking spray, and then transfer the popcorn to the bowl; set aside.
3. In a small saucepan, whisk together the brown sugar, corn syrup, butter, salt and water, and bring to a simmer over medium-high heat. Continue to simmer, stirring often, until the mixture reaches 250 degrees F on a candy thermometer, about 3 to 5 minutes.
4. Turn off the heat, and whisk in the vanilla and baking soda. Immediately pour the hot mixture over the popcorn. Use a rubber spatula to gently fold the caramel into the popcorn until all of the popcorn is coated. Gently stir in the peanuts, and transfer the mixture to the prepared baking sheet, spreading it out.
5. Bake for 1 hour, stirring every 20 minutes. Remove from the oven, and cool on a wire rack for 20 minutes. Gently break up the popcorn. Serve immediately, or store in an airtight container for up to 5 days.