- With the rack in the middle position, preheat the oven to 350°F (180°C). Line a baking sheet with a silicone mat or parchment paper.
- In a large pot over medium-high, heat the oil. Add the popcorn kernels and toss to coat in the oil. Cover. Reduce the heat to medium and pop the kernels while shaking the pot regularly. The popcorn is ready when you no longer hear any kernels popping. Transfer into a large bowl. Remove any kernels that have not popped. Wash out the pot.
- In the same pot over high heat, bring the syrup and butter to a boil until a candy thermometer reads 248°F (120°C). Remove the pot from the heat.
- Add the popcorn and pecans to the pot of caramel. Using a spatula, mix well to coat the popcorn in the caramel. Spread out on the baking sheet. Sprinkle with the fleur de sel.
- Bake for 10 to 12 minutes or until the popcorn no longer sticks to your fingers. Let cool. The popcorn will keep for 2 weeks in an airtight container at room temperature.