Pop the popcorn kernels using an air popper or on the stovetop. Place the popped popcorn in a large mixing bowl.

In a large pot over medium heat, combine the sugar, butter, and corn syrup. Stir until the mixture comes to a boil.

Continue to boil without stirring until the mixture reaches 300°F (hard crack stage) on a candy thermometer.

Remove from heat and stir in the vanilla extract and baking soda. The mixture will bubble up.

Quickly pour the caramel over the popped popcorn and stir to coat evenly.

Allow the mixture to cool slightly, then use buttered hands to form the popcorn into balls.

Place the popcorn balls on a baking sheet lined with parchment paper to set.