Preheat your oven to 350°F (175°C) and grease three 8-inch cake pans. In a large mixing bowl, whisk together the eggs, sour cream, and granulated sugar until smooth. In a separate bowl, sift the all-purpose flour, unsweetened cocoa powder, baking powder, baking soda, and salt. Gradually incorporate the dry mixture into the wet ingredients, stirring until just combined.

Mix the unsweetened cocoa powder and instant coffee with one cup of boiling water in a bowl. Stir until dissolved. Once the cocoa mixture cools slightly, gently fold it into the cake batter.

Evenly divide the cake batter among the three prepared pans and bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean. Allow the cakes to cool in pans for 10 minutes before transferring them to a wire rack.

Heat granulated sugar in a medium saucepan over medium heat until it melts and turns a golden amber color. Add butter and heavy cream, whisking until smooth. Stir in a pinch of salt and let it cool completely.

Beat together the softened cream cheese and unsweetened cocoa powder until creamy. Gradually add in powdered sugar, then melt dark chocolate over a double boiler and fold it into the creamy mixture along with heavy cream.

Level the cooled cakes with a serrated knife. Place the first layer on a cake stand, spread frosting on top, and drizzle with salted caramel sauce. Repeat with the second layer, and top with the final layer. Frost the entire cake.

Allow the cake to set for at least 30 minutes before slicing and serving.