Remove all unpopped kernels from popped popcorn. Put popcorn into a 17- x 11- x 2-inch baking or roasting pan. Set into oven on warm temp.

In a medium saucepan, combine sugar, corn syrup, and butter. Cook and stir over medium heat until mixture boils. Remove pan from heat. Stir in chocolate chips and vanilla until chocolate is melted.

Pour the hot chocolate mixture over popcorn; stir gently to coat.

Bake in a 300 degree F. oven for 45 minutes, stirring mixture gently every 15 minutes.

Spread on a large piece of foil. Cool completely.

Store coated popcorn tightly covered for up to one week.

Yield: 13 cups (1 cup per serving).  Excellent fudgy popcorn — makes a terrific treat.