1 C butter
2 C brown sugar
1/2 C light Karo syrup
1 tsp vanilla
1/2 tsp. baking soda
3 regular size bags microwave popcorn

Combine first three ingredients and bring to a good boil. Add vanilla and soda after mixture has cooled slightly. Stir and pour over popcorn, coating evenly.

Bake at 250°F for one hour, stirring every 15 minutes.