Preheat your oven to 225°F. Prepare two large baking sheets, lining them with silicone baking mats. If you only have one silicone mat, you can use parchment paper for the second sheet, though silicone mats yield the best results.

Use an air popper to pop your popcorn, avoiding additional oil.

Spread the popped popcorn evenly on one of the prepared baking sheets and set it aside.

In a medium saucepan, combine butter, brown sugar, and corn syrup over medium heat.

Whisk the mixture constantly until the butter melts and the brown sugar dissolves, approximately 3-5 minutes.

Continue whisking while adding vanilla extract, salt, and baking soda to the caramel. Expect some bubbling from the baking soda.

Once the caramel thickens and becomes lighter and fluffier, about 1-2 minutes, remove the saucepan from heat.

Quickly pour the caramel over the popcorn and use a spatula to thoroughly coat the popcorn.

Bake the caramel-coated popcorn in the oven, breaking it into three or four 15-minute intervals, for a total of 45-60 minutes.

Every 15 minutes, remove the baking sheet, toss the popcorn to ensure an even coat, and break up any clumps. At the 45-minute mark, check the popcorn's stickiness and coating.

Once baking is complete, transfer the caramel popcorn to the second baking sheet to cool, using a spatula to break up any lumps.

If you prefer salted caramel popcorn, sprinkle a bit of coarse salt over the popcorn while it cools.

Once completely cool, store the caramel popcorn in an airtight container.