Allow your oven to preheat to 300 degrees while you prepare the recipe.
Prepare two baking sheets by lining them with aluminum foil and spraying them lightly with non-stick cooking spray. Set them aside.
Get out your air popper and make some popcorn the old-fashioned way!
You need approximately 14 cups of popcorn, which comes from approximately ⅓ cup of un-popped kernels.
I pop the corn into a large bowl, shake the bowl vigorously to knock the unpopped kernels to the bottom of the bowl, and then transfer the warm popcorn into another large bowl by hand to ensure that all the unpopped and partially popped kernels are removed. (Seriously, there is nothing worse than chomping down on an unexpected hard kernel.)
Side the popped corn aside for a moment.
In a medium, microwave-safe bowl, or my preference a glass 4 cup measuring cup, heat the butter, brown sugar, molasses, salt, and corn syrup, DO NOT ADD THE BAKING SODA YET, just long enough to melt the butter. Stir well and put back in the microwave.
Heat in the microwave for about 3 minutes, allowing the mixture to boil for 2 minutes.
Now you add the baking soda!
This part is great because it's fun to watch while the mixture foams!
Pour the caramel mixture over the popped corn and mix well with a silicone spatula instead of a wooden spoon to coat every piece. The caramel won't stick to the silicone, making cleanup easier.
Divide the caramel popcorn between the two baking sheets, spreading it out into a single layer.
For a salty snack, sprinkle sea salt over the popcorn before baking.
Bake each baking sheet in the preheated oven (300 degrees) for 5 minutes.
Cool at room temperature and break into pieces.
Store in an air-tight container.