Start by popping the corn. Use an air-popper if you have one. You don't want to add any oil or butter to the popcorn while popping it, so an air popper would work best. An alternative would be to use your microwave. You can buy microwavable plain popcorn in most grocery stores. Once the popcorn is ready, spread it onto two baking sheets to cool. Add the pretzels. Set aside.

In a large sauce pan, on medium heat, bring to a boil the brown sugar, corn syrup, pumpkin spice, and butter. Swirl the pan to ensure the ingredients are mixing together and that the brown sugar is dissolving. Once the mixture comes to a boil, continue cooking for exactly two minutes. Remove the sauce pan from the heat and sit it into the kitchen sink. Add the baking soda and stir well with a wooden spoon. (I like to place the sauce pan in the sink just in case the addition of the baking soda results in some overflow - be careful, this caramel mixture is extremely hot!)

Poor half of this mixture over the popcorn onto each baking sheet. Sprinkle with salt, and using metal tongs, toss gently to coat.

Bake the mixture at 250 degrees for 1 hour. Remove the popcorn from the oven every 15 minutes, toss and place it back in the oven.

Once done, remove from the oven and remove the popcorn from the baking sheet and try to keep the popcorn in a single layer on parchment paper that’s been spread out on a large table. Allow to cool completely at room temperature. This will not take too long; about 30 minutes is good.

Once completely cooled, package or serve immediately!