Crispy Caramel Popcorn from The Bake-Off Flunkie 

2 cups packed brown sugar
1/2 cup light corn syrup
1 cup (2 sticks) butter
1/2 teaspoon cream of tarter
1 teaspoon salt
1 teaspoon baking soda
6 quarts popped corn (I used an air popper)
2 cups nuts, optional (I didn't use any nuts)

1. Heat your oven to 200 and spray two rimmed baking sheets with non-stick spray.

2. In a medium saucepan, combine the brown sugar, corn syrup, butter, cream of tarter, and salt. Bring to a boil over medium heat.

3. Clip on a candy thermometer and cook, stirring constantly (I actually didn't stir it at all--so much for reading the directions carefully) until the mixture reaches hard ball stage, about 5 minutes.

4. Remove from the heat and quickly whisk in the baking soda. Poor immediately over popped corn, and stir and toss gently until it's evenly coated. Divide the mixture between the two prepared pans and spread into an even layer.

5. Bake for 1 hour, stirring every 20 minutes. Turn out onto waxed paper and allow to cool completely (I actually let it cool on the pans, and I stirred it a few times as it cooled to break up the big chunks). Store in an airtight container.