Baked Caramel Corn (Gluten-Free)

You will need:

6 quarts of popped corn (this is 2/3 cup raw in an air popper)
1 cup butter
2 cups brown sugar
1/2 cup corn syrup
1 tsp salt
1 tsp vanilla
1/2 teaspoon baking soda
1 pound salted peanuts (optional)

Pop popcorn (don't add butter or salt) mix with peanuts (if using) in large bowl.
Preheat oven to 250 degrees F
 in 3 quart saucepan, melt butter over medium heat.
Stir in sugar, corn syrup and salt.
Bring to a boil, stirring constantly.
Boil without stirring 5 minutes or until soft-ball stage on candy thermometer.
Remove from heat and stir in vanilla.
Add baking soda all at once and stir vigorously (mixture will foam up!)
Pour over popcorn and mix well.
Divide popcorn into 2 large baking pans or roasters.
Bake at 250F for one hour, stirring every 15 minutes. Use a buttered wooden spoon if you have trouble with it sticking while stirring.
Let cool and store in airtight container (plastic bags work fine!). Does not need refrigeration.