Preheat the oven to 225°F (107°C) and toast pecans in a saucepan with hot vegetable oil until lightly toasted. Set them aside.
Pop the rest of the popcorn kernels in the same saucepan with a pinch of salt, cover, and shake occasionally until all kernels have popped.
In a separate saucepan, melt unsalted butter over medium heat. Add Karo corn syrup, light brown sugar, and salt. Let it boil and simmer for 3 minutes without stirring. Remove from heat, stir in baking soda and vanilla extract. Pour this caramel over the popped corn and pecans, coating them evenly.
Spread the caramel-coated mixture onto a parchment paper-lined baking sheet. Bake at 225°F for 45 minutes, stirring every 15 minutes.
Once done, cool completely before breaking it into clusters.