Preheat oven to 300F.
Heat oil in a large heavy bottomed stockpot or dutch oven over medium high heat. Add popcorn and cover with a lid. Using potholders or a towel to hold the handles, shake the pot around to keep the kernels moving as they pop. When several seconds pass between pops, remove from heat. Remove and discard any un-popped kernels and return popcorn to the pot it was popped in. Crush nori up into small flakes with your hands and add, along with sesame seeds, to the pot with popcorn.
Combine brown sugar, butter, salt, and corn syrup in a medium sauce pan. Cook and stir over medium heat until mixture begins to boil. Reduce heat to medium to maintain a moderate boil, and cook, without stirring, for exactly 5 minutes.
Remove pan from heat and stir in sesame oil, vanilla, and baking soda. Immediately pour caramel mixture over popcorn and gently toss toss toss to combine as quickly as you can. If you don’t work quickly the caramel will harden and become difficult to mix.
Spread popcorn in an even layer over a parchment lined baking sheet. Bake for 15 minutes, stir mixture around, and bake for 5 minutes more. Once cooled enough to handle gently toss the popcorn around so it doesn’t all stick together in one large block.
Store tightly covered for up to one week. It probably won’t last that long.
*variation: If you’re not sure about the nori but like a bit of heat, try skipping the nori and add a heaping tablespoon of sriracha along with the sesame oil and vanilla in the recipe.