1 cup butter, cut into pieces
1 cup sugar
2 (14 ounce) cans sweetened condensed milk
4 tablespoons light corn syrup
Prepare a 9 x 9 baking dish by lining with foil, and spraying liberally with cooking spray. Combine all ingredients in a medium saucepan over medium heat. Heat until butter is melted, stirring frequently. Increase heat to medium high, until the mixture comes to a simmer. Reduce heat to medium and simmer, stirring constantly, until caramel has turned a rich amber color and thickened slightly. This takes about 15-20 minutes. Pour into prepared pan and refrigerate for 15 minutes then sprinkle with fleur de sel and return to fridge until completely cooled.