Yummy Yogurt Popcorn

2 1/2 quarts popped popcorn
1 cup plain yogurt
1 cup brown sugar
1/3 cup light corn syrup

Put popped popcorn in a large bowl and keep warm. In a 2 1/2-quart saucepan, combine yogurt, brown sugar and corn syrup. Cook and stir over medium heat to hard ball stage (250 degrees F on candy thermometer). Pour over popped popcorn, stirring to coat.