Pop popcorn & salt (optional) set aside. Melt 1 cup of butter in a medium saucepan over medium heat. Add 1 cup of brown sugar and stir until thoroughly mixed. Stirring continuously, bring the butter and sugar mixture up to a boil on medium heat.
When it reaches a boil allow it to cook for 5 minutes without stirring on medium heat. Add the 2 tsp. of vanilla at the 4 minute mark and stir to mix.

Continue to boil for one addition minute and then add the 1/2 teaspoon of baking soda. Drizzle the caramel mixture over the popcorn. Use a spoon to gently fold the popcorn with the mixture until the kernels are all covered. Add peanuts if like. Pour the popcorn out onto a cookie sheet covered with aluminum foil. Let the popcorn cool.