Prepare an 11x13-inch baking pan with cooking spray; set aside.
In a double broiler* melt butter and chocolate; stirring frequently until melted. Remove from heat and stir in sugar, vanilla and salt. Whip in eggs one at a time until well incorporated. Beat in flour a little at time until mixture is glossy (about 1 minute). Set aside.
Homemade Salted Caramel Sauce
On medium low heat, mix together sugar and water until sugar has dissolved. If any crystals remain, use a wet brush to remove. Increase heat to high and occasionally swirl the mixture in the pot using the handle to keep it moving until mixture begins to bubble. Do not stir. Continue cooking and swirling for approximately 5-7 minutes until it resembles a medium amber color. Add butter and cream. The mixture will broil rapidly. Whisk to combine. Add salt and stir to combine. Remove from heat.
Salted Caramel Layer
Mix together all ingredients until well combined.
Divide brownie batter in half and set one portion aside and pour remaining batter into prepared baking dish.
Reserve 3/4 cup salted caramel; set aside. Pour remaining salted caramel on top of brownie mixture. Next, layer remaining brownie batter on top of caramel. Lastly, drizzle the 3/4 cup caramel to the top of brownie and using a skewer or knife, softly swirl it through brownie in circular motions creating a pattern on top.
Bake for 20-25 minutes in a preheated 400 degree Fahrenheit oven or until brownie begins to pull away from the sides.
Meanwhile, prepare an ice bath by filling a large pan or kitchen sink with ice cubes and water until about 3/4-inch deep. When the brownies are done, remove from oven and place in water bath allowing the brownies to cool completely before removing. (Yes, this really does help the brownie.)
*You can make your own double broiler by placing a bowl over simmering water