Closely adapted from Elisabet der Nederlanden. The recipe called for all semisweet chocolate, but given how sweet caramel is, I liked a mix of semi and bittersweet chocolates.
Lightly spray a 9X13 baking pan with oil and then line it with parchment paper. Be sure to leave an overhang of parchment paper on the sides.
Combine the cream and sweetened condensed milk in a small saucepan. Heat until warm and then turn off the heat. Cover the pan.
In a 3-4 quart saucepan with a heavy bottom, add the golden syrup, sugar and water. Place over high heat. Gently and briefly stir together and then clip a candy thermometer to the side of the pan.
Let the mixture come to a boil and do not stir again. Let it boil, around 15 minutes, until the candy thermometer registers 250 F.
When the caramel reaches 250 F, reduce the heat to medium and add the unsalted butter, bourbon and sea salt.
Stir the caramel continuously for about 15 minutes, until the caramel reaches 235 F.
When the temperature reaches 235 F, remove the caramel from the heat and add the vanilla bean paste and finely chopped chocolate. Stir until the chocolate is melted and the mixture is homogenous.
Pour the chocolate caramel mixture into the prepared pan, using a silicone spatula to scrape all of the caramel out of the pan. Use an offset spatula to quickly smooth the top of the poured caramel. Rap the pan once or twice onto the counter to settle the caramel.
Sprinkle the top of the chocolate caramel evenly with fleur de sel.
Let cool and set for about 3 hours--the caramel should be completely completely cool before you slice it.
Use the parchment paper overhang to take the caramel "cake" out of the pan and transfer it to a cutting board. Slice into bite sized squares or rectangles and then use wax paper to wrap each individual caramel.
I stored mine at room temperature, but if your house is warm you may need to store in the refrigerator, in which case let stand at room temperature for 15 minutes before serving.