Preheat your oven to 177 °C (175 °C). Grease two 8-inch round cake pans and line the bottoms with parchment paper rounds.

Prepare the salted caramel: Heat 240 ml of granulated sugar in a heavy-bottomed saucepan over medium heat, swirling occasionally until fully melted into an amber syrup. Whisk in 90 ml of cubed butter until incorporated, then slowly pour in 120 ml of warm heavy cream while whisking continuously. Boil for 1 minute, remove from heat, stir in 1 teaspoon of flaky sea salt, and set aside to cool and thicken.

In a large mixing bowl, whisk together the flour, 480 ml sugar, cocoa powder, baking powder, baking soda, and fine salt until evenly blended.

In a separate bowl, whisk together eggs, buttermilk, vegetable oil, and 1 teaspoon vanilla extract. Pour the wet ingredients into the dry ingredients and stir until just combined.

Gradually whisk in the hot brewed coffee until the batter is smooth and pourable. Divide batter evenly between the prepared pans.

Bake for 30 to 35 minutes, or until a toothpick inserted into the center emerges clean with a few moist crumbs. Let the layers cool in pans for 15 minutes, then invert onto wire racks to cool completely.

Make the fudge frosting: Beat softened butter in a stand mixer on medium-high speed for 3 minutes until pale and fluffy. Sift in powdered sugar and cocoa powder in alternating batches with 80 ml heavy cream and remaining vanilla. Mix in the melted, cooled chocolate and beat on medium-high for 2 minutes until glossy and silky.

Assemble the cake: Place one cooled layer on a serving plate. Pipe a thick border ring of chocolate fudge frosting around the perimeter of the cake top to create a dam. Spoon 80 ml of thickened salted caramel into the center and spread evenly. Top with the second cake layer.

Cover the top and sides of the cake with the remaining chocolate fudge frosting. Smooth with an offset spatula, drizzle additional salted caramel over the top, and finish with a light sprinkle of flaky sea salt.