Preheat oven to 350 degrees F. Grease and flour three cake pans and line the bottoms with parchment.
Whisk the flour, cocoa powder, baking soda, baking powder, and salt in a large bowl.
In a separate bowl, whisk the sugar, buttermilk, oil, eggs, and vanilla until smooth. Combine with the dry ingredients, then stir in the hot coffee last.
Divide the batter among the three pans and bake for 28 to 32 minutes, until a toothpick comes out clean. Cool completely.
Melt the butter in a skillet and toast the kataifi over medium heat, tossing continuously, until deep golden, 8 to 10 minutes. Cool completely.
Melt 2 ounces of the couverture chocolate and toss the cooled kataifi in it to coat. Let set for 10 minutes at room temperature.
Combine the pistachio cream, tahini if using, and salt. Fold in the chocolate-sealed kataifi.
Heat the heavy cream until simmering, pour over the remaining chopped chocolate, let sit 2 minutes, then stir until smooth.
Layer the cake with the pistachio kunafa filling between each layer.
Pour the ganache over the top, letting it drip down the sides, and top with crushed pistachios before it fully sets.