Bake the banana cake as directed and allow it to cool completely. While it cools, prepare the caramel sauce.

Ensure all caramel ingredients are measured and ready to use. In a medium saucepan, combine sugar, water, and fine sea salt.

Place the pan over medium-high heat and whisk continuously until the mixture begins to boil. Allow it to boil without whisking until it turns a deep amber color, swirling the pan occasionally for even caramelization.

Carefully whisk in the butter until fully incorporated, then remove the pan from heat. Gradually whisk in the heavy cream (be cautious, as it will steam—use a long-handled whisk for safety). Stir until the mixture is smooth.

Let the caramel cool for a few minutes, then transfer it to a glass bowl or jar and refrigerate until completely chilled.

Whip the butter in a mixing bowl until light and fluffy. Add the powdered sugar, 1/2 cup of the chilled caramel sauce, sea salt, and vanilla extract.

Mix until the frosting is well combined and slightly fluffy. If needed, chill the frosting until it reaches a firmer consistency.

Spread half of the frosting over the first layer of the cooled cake. Drizzle and spread a generous spoonful of caramel sauce over the frosting.

Place the second layer of cake on top and spread the remaining frosting evenly over the surface.

Before serving, top the cake with diced bananas* and chopped nuts, drizzle with the remaining caramel sauce, and finish with a sprinkle of shaved chocolate and coarse sea salt.