Allred Family Carmel Corn

1 c. butter (2 sticks) 2 c. firmly packed brown sugar 1/2 c. corn syrup 1 tsp. salt 1/2 tsp. baking soda 1 tsp. vanilla 6 qt. popped corn Melt butter. Stir in brown sugar, corn syrup, and salt. Bring to boil, stirring constantly. Boil with stirring 5 minutes. Remove from heat. Stir in soda and vanilla. Gradually pour over popped corn, mixing well. Turn into 2 large greased baking pans. Bake at 250 degrees for 1 hour, stirring every 15 minutes. Remove from oven. Cool completely. Break apart and store in tightly covered container. Makes about 5 quarts caramel corn.