Salted Caramel Popcorn

Position 2 oven racks evenly in the oven and preheat the oven to 225°F. Line 2 rimmed baking sheets with parchment paper. 

In a large, heavy saucepan or pot, warm the oil over medium-high heat.

Add the corn kernels, swirl the pot to coat them with oil, then cover the pan.

Pop the corn, shaking the pot occasionally to prevent burning or sticking.

When the popping sounds slow down the popcorn is ready. Pour the popcorn into a large metal or other heatproof bowl, discarding any un-popped kernels. 

To make the caramel, in a heavy saucepan, melt the butter over medium heat. Add the brown sugar and corn syrup. Cook, stirring constantly with a whisk, until the sugar melts and the mixture boils. 

Continue to boil until thickened, whisking occasionally, about 3 minutes (be careful not to let it burn).

Remove from the heat and stir in the vanilla, fine sea salt, and baking soda. Stir with a whisk to combine, then immediately pour over the popcorn.

Using a heatproof rubber spatula and moving quickly, stir the popcorn until evenly and well coated with the caramel (be careful because the caramel is very hot).

 Pour it onto the baking sheets, dividing it evenly.

Spread out the popcorn into an even layer and sprinkle with the coarse sea salt. 

Bake for 45 minutes to 1 hour, stirring 3 or 4 times during baking.

Let cool completely in the pans on a wire rack, then break apart and serve.