Ingredients

• Banana Layer:
• 1/4 cup butter, softened
• 3/4 cup white sugar
• 1 egg
• 1/2 cup sour cream
• 1/2 teaspoon vanilla extract
• 1 cup all-purpose flour
• 1/2 teaspoon baking soda
• 1/8 teaspoon salt
• 1/2 cup mashed ripe bananas
• Brownie Layer:
• 1/2 cup (1 stick) unsalted butter
• 5 oz oz dark chocolate, finely chopped
• 1 cup packed light brown sugar
• 1/2 cup all-purpose flour
• 1/8 teaspoon salt
• 2large eggs
• 1 teaspoon vanilla extract
• Caramel Layer:
• 1 1/2 cups sugar
• 1/4 cup light corn syrup
• 1 cup heavy cream
• 5 tablespoons unsalted butter
• 1 teaspoon fine fleur de sel, plus extra for sprinkling
• 1/2 teaspoon pure vanilla extract

Instructions

1. Preheat oven to 350. Grease a 9 x 13 inch baking pan and set aside.
2. Banana Layer: In a large bowl, cream together the butter and sugar until smooth. Beat in the eggs, one at a time, then stir in the sour cream and vanilla. Combine the flour, baking soda and salt; stir into the batter. Finally, mix in the mashed banana. Spread evenly into the prepared pan.
3. Start the Brownie Layer: Add the 1 stick of butter to a medium saucepan and set over medium heat. Melt the butter, and continue to heat until the butter sizzles. At that point, add the chocolate to the pan and gently shake the pan to submerge in the butter. Turn off the heat and set aside.
Begin Caramel:
4. In a deep saucepan, combine 1/4 cup water, the sugar and corn syrup and bring them to a boil over medium-high heat. Boil until the mixture is a warm golden brown. Don't stir -- just swirl the pan. (Can take a few minutes for the sugar to caramelize- keep an eye on it and continue to the next step.)
5. In a small saucepan simmer the heavy cream and butter and sea salt until the butter is melted. Set aside. To finish the caramel: when sugar mixture is a warm golden brown, turn off the heat and carefully add the cream mixture. Stir in the vanilla with a wooden spoon and cook over medium-low heat for about 10 minutes, until the mixture reaches 248 degrees F (firm ball) on a candy thermometer.
6. During those 10 minutes finish the brownies: In a large bowl, using an electric mixer, mix the brown sugar, flour and salt just until evenly combined. Add one of the eggs to the bowl and beat just until incorporated then scrape down the sides of the bowl and add the remaining egg, again beating just until incorporated. (Don't overmix!) Mix in the vanilla. Whisk the butter and chocolate mixture until smooth then add to the mixing bowl. Stir to incorporate with a rubber spatula.
7. Once the caramel is done, pour it carefully over the banana batter in the 9x13 pan. Follow with the brownie batter- which will need to be poured over the other layers as evenly as possible, and then spread over the caramel as best as you can. Don't worry too much as it will all swirl together as you bake it.
8. Bake for 35-40 minutes. or until a toothpick comes out with a few moist crumbs. Cool completely before cutting.

Notes