fleur de sel (this is a coarse salt, see note below)
NOTE: Fleur de sel ("flower of salt" in French; French pronunciation: [flœr də sɛl]) or flor de sal ("flower of salt" in Portuguese, Spanish and Catalan) is a hand-harvested sea salt collected by workers who scrape only the top layer of salt before it sinks to the bottom of large salt pans. Traditional French fleur de sel is collected off the coast of Brittany, most notably in the town of Guérande (Fleur de Sel de Guérande being the most revered), but also in Noirmoutier, Île de Ré and Camargue.
Caramelize the sweetened condensed milk by immersing a closed can of sweetended condensed milk on its side in a pot of water and bring to a boil.
Simmer or light boil for 2 to 2 1/2 hours, topping off with water as needed. NOTE: Be careful and don’t allow water to dry out; can could explode.
Remove from heat and cool thoroughly before opening. DO NOT open the can while its still hot. The condensed milk should be thick and a nice caramel color.
You can do this a day ahead.
Combine caramelized milk, sugar, corn syrup and water in a medium sauce pan. Heat over a medium/high heat, stirring continuously until it reaches a deep amber color about 20 minutes. It will also be pretty thick. Remove from heat and slowly stir in heavy cream and then add Fleur de Sel. Whisk in sour cream; set aside to cool.
Preheat oven to 350 degrees.
Prepare 9 x 13-inch baking pan with bakers choice spray or butter. Line bottom of pan with parchment paper. Lightly spray parchment paper with bakers choice or lightly butter; set aside.
In a medium bowl; whisk together flour, salt and cocoa powder; set aside.
Place chocolate and butter in bowl of double boiler. Set over simmering water, stirring occassionally until completely mealted and combined. Turn heat off and leave bowl over hot water; add both sugar and brown sugar. Whisk until completely combined. Remove bowl from hot water. it should be room temperature. If not, allow to cool a few minutes.
When chocolate is at room temperature; add three eggs and whisk just until combined. Add remaining two eggs and whisk just until combine. Add vanilla and stir until combined being care to not overbeat batter at this point or you will have a dry brownie.
Gently fold dry ingredients into chocolate mixture, again do not over mix. NOTE: All this mixing is done by hand.
Spread 1/2 of the brownie mixture in bottom of prepared pan. In a zig zag fashion, drizzle/pour caramel over brownie mixture (this mixture is thick), taking care to not allow the caramel to touch sides of pan as it will burn. Spread evenly over brownie mixture, again ensuring caramel does not touch pan. Drop heaping spoonfuls of remaining brownie mixture over caramel mixture; spread evenly over caramel mixture to edges of pan.
Bake for 30 to 35 minutes. Top with begin to look like it's drying out a little around the edges when done. Remove from oven. Sprinkle top of brownies with 1 1/2 tsp Fleur de Sel and 1 tsp coarse sugar.
Allow browines to completely cool before cutting. Store wrapped in plastic for up to 4 days.