Preheat oven to 250°F
In a large pot, heat oil over medium heat. Add popcorn kernels, cover, and pop. Transfer popped popcorn to a large aluminum hotel pan or roaster pan, removing any unpopped kernels
In a saucepan over medium heat, combine butter, sugar, corn syrup, and salt. Bring to a boil, stirring occasionally
Continue boiling until the mixture turns a light amber color, about 4–6 minutes
Remove from heat and carefully stir in vanilla and baking soda (the mixture will foam)
Immediately pour caramel over the popcorn and stir well to coat evenly
Bake for 40–50 minutes, stirring every 10 minutes, until crisp and evenly coated
Cool completely before breaking apart and serving
