Preheat the oven to 325°F and spread the pecan halves on a baking sheet. Toast for 6 to 8 minutes until fragrant and slightly darker.

Line a 9x9 inch baking pan with parchment paper, leaving a slight overhang on two sides for easy removal.

In a heavy-bottomed saucepan over medium heat, melt the unsalted butter, then add light brown sugar and granulated sugar. Stir constantly for about 2 minutes until the mixture is smooth.

Continue cooking without stirring while monitoring with a candy thermometer. Cook until the mixture reaches 295 to 305°F, about 8 to 10 minutes.

Remove the saucepan from heat and quickly stir in the sea salt and vanilla extract.

Add the baking soda and stir vigorously for about 10 seconds until the mixture becomes light and foamy.

Immediately fold the toasted pecans into the candy mixture, stirring quickly to coat all the nuts.

Pour the mixture into the prepared pan and spread it roughly into an even layer. Let cool at room temperature for at least 2 hours before cutting or breaking into pieces.