• Preheat the oven to 180 (350f) and prep a 10 inch springform pan with cooking spray and parchment paper.
• In a large mixing bowl add the sugar, vanilla extract, salt, mayonnaise, buttermilk, and sifted cocoa powder, and mix with a whisk until well combined.
• Add the flour, baking powder, and baking soda, and mix with a whisk until almost combined.
• Add the hot coffee and mix until you get a smooth batter without lumps of flour.
• Pour the batter into the prepared baking pan and bake the cake in a 180c (350f) preheated oven for about 40 minutes or until a toothpick inserted into the cake comes out clean with a few moist crumbs.
• Allow the cake to cool to room temperature for at least an hour to prevent the frosting from sliding off the cake.

Make the chocolate fudge frosting

• Into a saucepan, add the butter, heavy cream, and dark chocolate, and sift the cocoa powder and powdered sugar, and kosher salt.
• Heat all the ingredients over medium heat mixing constantly until the mixture is smooth and melted.
• Strain the mixture into a large bowl or baking pan to speed up the cooling process.
• Cover the top with plastic wrap so that the plastic wrap is directly touching the top of the frosting. This will prevent skin from forming.
• Let it cool at room temperature for 30 minutes, and then transfer it to the fridge to cool for another 1-2 hours. (depending on the thickness you are looking for)
• Remove the frosting from the fridge and give it a mix with a spoon or a spatula. Spread a thick layer of the frosting on the cooled cake and make swirls using an offset spatula.