1 teaspoon fine fleur de sel, plus extra for sprinkling
½ teaspoon pure vanilla extract
Line an 8-inch-square baking pan with parchment paper, allowing it to drape over 2 sides, then brush the paper lightly with oil.
In a deep saucepan, combine ¼ cup water, the sugar and corn syrup and bring to a boil over medium-high heat. Boil until the mixture is a warm golden brown (about 10 minutes.) Don't stir -- just swirl the pan. Watch closely as it will turn burn quickly once it starts to turn brown.
In the meantime, bring the cream, butter and 1 teaspoon of fleur de sel to a simmer in a small pot over medium heat. Turn off the heat and set aside.
When the sugar mixture is done, turn off the heat, attach your candy thermometer to the pot and slowly add the cream mixture to the sugar mixture. Be careful -- it will bubble up. Stir in the vanilla with a wooden spoon and cook over medium-low heat for about 10 minutes. Take it off heat when the mixture reaches 248 degrees F (firm ball) on a candy thermometer.
Very carefully (it's hot!) pour the caramel into the prepared pan and refrigerate for a few hours until firm.
When the caramel is cold, pry the sheet from the pan onto a cutting board. Cut the square into pieces and sprinkle with fleur de sel. Wrap in 4 by 5 inch pieces of parchment paper and refrigerate. Serve well chilled.
Recipe by Garnish with Lemon at http://www.garnishwithlemon.com/fleur-de-sel-caramels/