Preheat oven to 350°F (175°C). Grease and flour two 8-inch (20 cm) round cake pans and line bottoms with parchment paper.

Whisk together cocoa powder and hot coffee in a medium sized bowl and set aside.

In a large mixing bowl, combine flour, sugar, baking soda, baking powder and salt. Add eggs, buttermilk, melted butter and vanilla extract and beat on medium speed for 3 minutes. Scrape sides of bowl as needed. Stir in coffee and cocoa mixture. The cake batter will be very runny.

Divide batter between the two cake pans and bake for 32-35 minutes, until cake is springy when touched and no dent is left behind. A wooden toothpick tester must come out clean.

Cool cakes completely in pans on wire racks. When cakes are no longer warm, cover the pans tightly with plastic wrap or aluminum foil and chill for at least 2 hours.

Measure all ingredients and place them near the stove. Heat sugar over medium high heat in a medium-sized, heavy-bottomed saucepan with high sides. Once sugar begins to melt, gently stir with a heatproof spatula or whisk to help it heat evenly.

When (nearly) all of the sugar has melted and liquid is amber (caramel) colored, add the butter and stir until it has completely melted.

Remove from heat and stir in the cream. CAUTION, the mixture will foam up considerably and possibly splatter. Keep stirring until caramel sauce is smooth. You made need to return it to the heat to help any crystals dissolve.

To eliminate any undissolved crystal lumps, pour sauce through a wire sieve into a heatproof bowl. Stir in vanilla and salt.

Allow the caramel sauce to cool to room temperature. It will thicken as it cools. Gently warm caramel sauce as needed before serving.

Make Ganache Frosting ahead of time as it needs about 2 hours to cool.

In a medium-sized saucepan, heat and stir the cream, butter, sugar and salt over low heat until sugar dissolves and mixture nearly comes to a boil. Do not allow it to boil. Remove from heat and stir in chocolate until completely smooth. Stir in vanilla.

Allow mixture to cool to room temperature, until it has thickened into a pudding-like spreadable consistency, stirring occasionally. You can help this process along by chilling the ganache for 10-20 minutes if necessary. If the ganache hardens too much, you can warm it slightly.

Cut your cold butter into 1-inch (2 cm) cubes and allow it to stand at room temperature for about one hour. Butter should be softened but not greasy-looking. If your kitchen is very warm and the butter looks like it’s on the verge of melting, chill it while you prepare the meringue.

It is essential that no grease or fat comes into contact with the egg whites. Even a trace of fat will prevent the egg whites from whipping into stiff peaks. Use a very clean metal or glass mixing bowl. Separate the eggs one at a time into a small bowl, add the egg white to the mixing bowl and separate the next egg. That way, if a yolk does break, only one egg goes to waste (or becomes an omelet later), and not all of them.

Add the sugar to the egg whites and place your mixing bowl over a pot of simmering water, making sure the bowl does not touch the water. Whisk the egg whites lightly while the meringue is heating. After a few minutes, you can test whether the mixture is ready by rubbing it between your fingers. If there is no graininess and the sugar is dissolved completely, remove from the heat and add a pinch of salt.

Using the whisk attachment of your stand mixer or an electric hand-held mixer, beat the egg whites on medium to medium-high speed for about 10 minutes until the bowl feels completely cool and a very thick, glossy, bright white meringue with stiff peaks forms. This can take up to 20 minutes. If the meringue is still too soft after 20 minutes of beating, put the bowl into the fridge for about 10 minutes and then try whipping again. If the chilling doesn’t help, some fat has probably got into the egg whites and you will need to discard the mixture and completely start over.

Once the buttercream is fluffy and creamy, beat in vanilla and six tablespoons of cooled salted caramel sauce.

Turn chilled cakes out of the pans and remove parchment paper. If you wish, you can level the cakes, horizontally cutting off the domed or uneven tops. Slice each cake in half horizontally so that you have four layers. Ideally, you would use a cake leveler to accomplish this but a long, serrated bread knife works as well.

Place the bottom layer (the bottom half of one of the cakes) on a cake platter and lay strips of parchment paper under the edges to help keep the platter clean.

Spread cake with about a quarter of the salted caramel buttercream, then drizzle with 1-2 tablespoons of salted caramel sauce. Place the next layer on top and repeat until you have your final layer of cake on top (the bottom half of the second cake, upside-down).

Using the remaining buttercream, you’re going to crumb-coat the cake. Start by frosting the sides of the cake. Holding your palette knife parallel to the cake, apply plenty of buttercream to the sides, filling in any holes and uneven spots with the buttercream. It’s ok if it doesn’t look perfect or you get crumbs in the buttercream, just try to spread it evenly. Place the entire cake in the fridge for 30 minutes.

Take the cake out of the fridge and cover it with the ganache frosting. As before, start with the sides, spreading and smoothing the ganache frosting with a palette knife. Then frost the top of the cake. Remove the parchment strips from under the edges of the cake and wipe the platter clean, if necessary.

Finally, finish by drizzling salted caramel sauce over the top of the cake, in a spiral pattern if you like, allowing the sauce to drip down the sides.

Serve cake slices with additional salted caramel sauce if desired.

Store cake in the refrigerator, tightly covered, in a cake carrier or a cake keeper if possible, for up to four days. Allow cake to stand at room temperature for one hour before serving for best flavor and consistency.