1. Combine the brown sugar, butter and corn syrup in a stainless steel pot. Bring to a boil stirring occasionally. Cook for 4 minutes at a boil. (The pot you use needs to be twice the volume of the mixture at a boil.)
2. Remove the mixture from the heat then add the baking soda, vanilla and salt. Stir quickly. The baking soda will expand, doubling the mixture in size. Use care this is very hot.
3. While very hot drizzle the caramel over the popcorn in a large bowl. Stir to coat.
4. Place the caramel covered popcorn on 2 sheet pans covered with parchment paper. Spread it out. Bake at 250 degrees for 1 hour stirring every 15 minutes. It’s a drying process.
5. Remove from the oven. Allow to cool then break it into smaller pieces.