Ice Cream Popcornwiches

2 1/2 quarts popped popcorn
1 1/2 cups light brown sugar
3/4 cup dark corn syrup
1/2 cup butter
1 tablespoon vinegar
1/2 teaspoon salt
1 (6 ounce) package chocolate chips
1/2 cup chopped walnuts
2 pints brick-style vanilla ice cream

Keep popcorn warm.

In a 3-quart saucepan, combine brown sugar, corn syrup, butter, vinegar and salt. Cook and stir until sugar dissolves. Continue to cook until hard ball stage (250 degrees F on candy thermometer). Pour syrup over popped popcorn; stir to coat. Add chocolate chips and nuts; stir just to mix. Pour into two 13 x 9 x 2-inch pans, spreading and packing firmly. Cool.

In each pan, cut 12 rectangles. Cut each pint of ice cream into 6 slices. Sandwich ice cream between two popcorn rectangles.