Directions for Brownies
1. Preheat the oven to 350℉. Line a 9 x 13 x 2-inch baking pan with parchment paper or nonstick foil.
2. In a medium saucepan, melt the butter over medium-low heat, about 5 minutes, add the chocolate chips and remove from the heat. Let the chocolate sit in the warm butter for 3 to 5 minutes, and then mix together until smooth. Stir in the granulated and brown sugars and vanilla extract.
3. Add the eggs, one at a time, mixing well after each addition. Add the kosher salt, flour and cocoa powder. Mix until just combined. Pour batter into the prepared pan.
4. Dollop spoonfuls of caramel sauce on top of the brownies and swirl into the batter using a knife. Sprinkle the top of the brownie batter with the flaked salt. Bake for 25 - 30 minutes and a cake tester inserted into the middle comes out with a few moist crumbs. The center might look slightly undercooked, but will firm upon cooling. Cool completely before cutting into squares.
Directions for Caramel Sauce
1. Combine the sugar, corn syrup and water in a medium saucepan. Bring to a boil over medium-high heat, stirring until the sugar has dissolved, 5 minutes. Reduce the heat to medium-low. Continue to cook until the sugar mixture is a dark, golden brown, 10 to 15 minutes, and the mixture reaches 300℉ on a candy thermometer.
2. Remove the saucepan from the heat and add the heavy cream. The mixture will bubble up and the sugar will harden. Return the pan to the heat. Whisk until the sugar melts, 2 to 5 minutes, the mixture comes to a boil and the caramel is smooth. Remove from the heat and allow to cool for 15 minutes.
3. Add the creme fraiche, salt and vanilla to the caramel and whisk until well combined. Pour into jars and store in the refrigerator for up to 2 months.