Caramel Topping
1-Make the caramel filling first so that: Make the caramel filling first so that it can thicken up before we use it to top the brownies.
2-Heat 2/3 cup of sweetened condensed milk,: Heat 2/3 cup of sweetened condensed milk, 1/4 cup butter, 1/4 cup packed brown sugar, and 2 Tbsp light corn syrup over medium heat in a heavy saucepan. Stir frequently and let the mixture just begin to bubble (if you have and are using a candy thermometer, cook until the mixture hits 212°F/100°C). It will start bubbling up on the sides of the pan first. Once this happens, turn the heat down to low to let the caramel simmer.
3-Continue to stir frequently until the mixture: Continue to stir frequently until the mixture thickens and becomes a medium caramel color (about 5-7 minutes). You should be able to drag a spatula through the mixture and see the bottom of the pan for a second once it’s ready. Remove from the heat and stir in 1 tsp vanilla extract and 1/2 tsp fine salt.
4-Pour into a separate container, then set: Pour into a separate container, then set aside to cool to room temperature. If you make this in advance, cover the bowl and store it at room temperature overnight or in the fridge for up to a week. If you refrigerate the caramel, heat it in the microwave in short 15-second intervals until it reaches room temperature and is a more workable consistency.

Shortbread Crust
5-Preheat the oven to 350°F/175°C: Preheat the oven to 350°F/175°C. Line an 8×8-inch square baking pan with parchment paper. Set aside
6-Use a fork or pastry cutter to: Use a fork or pastry cutter to combine 1/2 cup butter, 1 cup flour, 1/4 cup powdered sugar, and 1/4 tsp fine salt.
7-Press into the bottom of the prepared: Press into the bottom of the prepared pan with your fingers. Prick the crust thoroughly with a fork, then bake for 22-25 minutes, or until the edges are just starting to brown.
8-Place the pan on a wire rack: Place the pan on a wire rack to cool. Keep the oven on, but lower the temperature to 325°F/163°C.

Brownie Batter
9-While the cookie crust bakes and cools,: While the cookie crust bakes and cools, make the brownie batter. In a medium bowl, mix together 1 1/2 cups of sugar, 3/4 cup of flour, 2/3 cup of cocoa powder, 1/2 cup of powdered sugar, 1/2 cup of chocolate chips, and 1/2 tsp of salt.
10-In a large bowl, whisk together 2: In a large bowl, whisk together 2 large eggs, 1/4 cup vegetable oil, 1/4 cup melted butter, 2 Tbsp water, and 1 tsp vanilla.
11-Pour the dry mix into the wet: Pour the dry mix into the wet ingredients and stir until just combined. The mixture will be pretty thick, but that’s how it’s supposed to be!
12-Pour the batter over the shortbread crust: Pour the batter over the shortbread crust in the prepared pan and smooth it into an even layer. Bake at 325°F/163°C for 38-43 minutes. You’ll know they’re done when they have a set outer edge and a slight jiggle in the center, or when a toothpick inserted halfway between the edge and center comes out with moist crumbs, not batter.
13-Set on a wire rack to cool: Set on a wire rack to cool fully before topping. If you want to accelerate the process, place the pan in the freezer for 30 minutes.

Chocolate Ganache Topping
14-Make the chocolate ganache as the brownies: Make the chocolate ganache as the brownies bake and cool because it needs time to cool and thicken before we top the brownies with it.
15-Heat 1/2 cup of heavy cream in: Heat 1/2 cup of heavy cream in a heatproof bowl in the microwave for 45 seconds, until it’s just beginning to bubble.
16-Gently pour 2/3 cup of dark chocolate: Gently pour 2/3 cup of dark chocolate chips into the heavy cream. Make sure the chips are fully covered with cream. Let the mixture sit for 1 minute. If you want to use milk chocolate to make the ganache, use 1/3 cup (80g) of heavy cream and 1 1/3 cups (240g) of milk chocolate.
17-Stir slowly until the cream and chocolate: Stir slowly until the cream and chocolate combine and the mixture is smooth. If any bits of chocolate aren’t fully melted, heat the mixture again for 15 seconds and stir until smooth.
18-Mix in 2 Tbsp of room temperature: Mix in 2 Tbsp of room temperature unsalted butter, 1 Tbsp corn syrup, and 1/4 tsp fine salt until combined.
19-Cover with plastic wrap to prevent the: Cover with plastic wrap to prevent the ganache from forming a skin, then set aside to cool to room temperature. If you need to make this in advance, it can be covered and stored in the fridge for up to a month. If you want to accelerate the cooling process, place the bowl in the fridge.

Decorating These Millionaire Brownies
20-Once the brownies are fully cooled, scoop: Once the brownies are fully cooled, scoop the room-temperature caramel on top and spread it into an even layer.
21-Then spread the room-temperature chocolate ganache on: Then spread the room-temperature chocolate ganache on top of the caramel.
22-Add a sprinkle of flakey sea salt,: Add a sprinkle of flakey sea salt, then use a sharp, warm knife to cut into the chilled brownies. Clean the knife after each cut to get perfect slices. Leftover brownies can be kept at room temperature in an airtight container for 2 days or in the fridge for up to a week.