Here's my family favorite.
1 c. brown sugar
2/3c. sweetened condensed milk
1/2 tsp. vanilla
1/2 c. light corn syrup
4 Tbsp. butter or margarine
5 qts. popped corn
candy thermometer
Melt together butter, brown sugar and corn syrup, stirring constantly, bring to a boil.Stir in the sweetened condensed milk and simmer to soft ball stage or 235°. Remove from heat and stir in vanilla. Pour over popped corn, stir thoroughly. Butter your hands and form into balls. Enjoy.