This recipe is for a big batch, but you can easily half it.
2 c unpopped popcorn, popped (Unsure of the amount of popcorn. I eyeball it. I fill 2 big Tupperware bowls. I think they are 8 qt size)
2 c packed brown sugar
1 c margarine or butter
1 tsp salt
1/2 Karo syrup
1 tsp vanilla
1/2 tsp baking soda
Melt margarine over med high heat, add brown sugar, karo syrup and salt. Bring to a boil, reduce heat to med and boil 5 minutes, stirring occasionally. Remove from heat.
Add vanilla and baking soda. Stir to dissolve.
Pour immediately over the popped popcorn. You will need a large roasting pan for it.
Bake at 250 for an hour. Stir the popcorn every 15 minutes.
Cool and enjoy!