Preheat the oven to 250ºF.

In a large sauté pan set over medium-low heat, cook the bacon until a majority of the fat has rendered and the bacon is crisp. Using a slotted spoon, transfer the bacon pieces to a paper towel-lined plate and reserve the bacon drippings.

Add 1 tablespoon of the reserved drippings, plus the vegetable oil, to a large stock pot over medium heat.

Add the popcorn to the pot and cover it. Once you hear the first kernel pop, remove the pot from the heat for 1 minute. Return the covered pot to the heat, shaking it over the flame until all of the kernels have popped. (It may take up to 5 minutes for all of the popcorn to pop.) Transfer the popcorn to a large bowl, sprinkle in the cooked bacon pieces, tossing to combine, and set the bowl aside.

Melt the butter in a medium saucepan over medium heat. Stir in the brown sugar, corn syrup and salt. Bring the mixture to a boil, stirring constantly. Then allow the mixture to boil, undisturbed, for 4 minutes. Remove the caramel from the heat and carefully stir in the baking soda and vanilla extract. (The caramel will bubbly vigorously once you add the vanilla.)

Immediately pour the caramel over the popcorn, stirring to coat the popcorn and bacon.

Transfer the coated popcorn into two 9x13-inch shallow baking pans.

Bake the caramel corn for 1 hour, stirring every 15 minutes.

Remove the caramel corn from the oven and spread it onto a parchment paper-lined baking sheet to cool completely before breaking it into pieces and serving.