6 qt. popped popcorn (3 bags microwave is same as 6 qtsp.)
2 sticks butter
1/2 c. light or dark corn syrup
1/2 tsp. baking soda
2 c. light or dark brown sugar
1 tsp. salt (omit if you use microwave popcorn)
1 tsp. vanilla

In a saucepan, melt butter and stir in brown sugar, corn syrup and salt. Allow to boil 5 minutes without stirring. Remove from heat; stir in soda and vanilla. Gradually pour over popcorn, mixing well. Pour in buttered baking pan and bake at 250°F for 1 hour, stirring every 15 minutes. Remove from oven. Cool completely. Break apart and store in covered container. (Be sure to separate popped corn from unpopped kernels.) It's also best to use a large shallow pan or 2 (11 x 13 x 9-inch) cake pans.