Place your popped popcorn in a large brown paper grocery bag and set aside

In a medium-sized sauce pan combine butter, sugar, salt and Karo Syrup and bring to a boil. Boil for 2 minutes and remove from the heat. Stir in the vanilla and baking soda, stirring constantly. At this point, the addition of the baking soda will cause the caramel to bubble, lighten in color, and increase in volume so don’t worry and think that you messed up.

Immediately pour the caramel over the popcorn in the paper bag, fold over the top of the bag, and shake the bag vigorously for 30 seconds or so. Now, put the bag in the microwave and let it cook for 1 minute. Once finished, take it out and shake for another 30 seconds. Repeat putting it in the microwave and shaking 2 more times for a total of 3 minutes in the microwave. After the final shake, pour the popcorn out onto a baking sheet and allow to cool and become crunchy.