Popcorn Balls

2 quarts popped popcorn

1 cup packed brown sugar

1/3 cup water

1/3 cup dark corn syrup

1/4 cup butter

1/2 teaspoon salt

1 teaspoon vanilla extract

Place popcorn in a large bowl; set aside. In a heavy saucepan, combine brown sugar, water, corn syrup, butter, and salt. Bring to a boil over medium heat, stirring constantly. Continue cooking, without stirring, until a candy thermometer reads 270 degrees (soft-crack stage). Remove from the heat; stir in vanilla. Pour over popcorn; stir until evenly coated. When cool enough to handle, quickly shape into balls.