Preheat the oven to 350°F (180°C) and line, with parchment paper, two round cake pans of about 8.5 inches in diameter.
In a big bowl sift together the flour, cocoa powder, salt and baking soda.
In a small bowl, pour the buttermilk and stir in the coffee powder.
In a big bowl, place the butter and sugar, and beat using a mixer for about 8 minutes or until the mixture turns whiter in color and gets fluffy.
Addn in one egg at a time, beating after each addition. Now mix in the mayonnaise.
Now beat in a third of the dry ingredients mixture, then add half of the buttermilk and coffee and mix, then the secind third of the flour, then the rest of the buttermilk and lastly the remaining third of the flour mixture, mixing in between each addition. Scrape down the bowl using a rubber spatula if needed when doing this.
Using the rubber spatula fold in the chocolate chips into the batter.
Pour half of the batter into one of the cake pans and the rest in the second one. Bake at 350°F (180°C) for about 35 minutes, or until a wooden stick comes out clean after inserting it.
Let the cakes cool down for 12 minutes, and only then turn them out by flipping them onto a plate.
To make the filling, place the heavy cream in a pan on the stove over medium heat, stiring with a spoon nonstop for about 3 minutes until the cream is hot. Quickly pour it into a small bowl and add in the chocolate chips, mixing with the spoon until the ganache takes form. Lastly stir in the salt. Let it cool down for a few minutes and then put it in the fridge for about 10 more minutes.
Place one of the cakes on a plate or cake stand (you can put some dulce the leche underneath to help the cake stay still), Now spread the dulce de leche on top, you can either do this by using a pippin pastry bag or just a spoon, just make sure the it is evenly spread.
Place the second cake on top, pushing it down a little. Here we recommend you refrigerate it for a few more minutes if its hot where you live, or you can go on to the next step.
Take the ganache out of the fridge and using a spoon add some on top and work your way down and then to the sides, either using the spoon or an angled spatula. We like it to be simple, you can add some chocolate chips on top, cocoa, some other chocolates, etc, you decide.
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