Preheat oven to 350°F (175°C). Grease three 8-inch round cake pans and line bottoms with parchment paper.
In a large bowl, whisk together flour, cocoa powder, granulated sugar, brown sugar, baking soda, baking powder, and salt.
In another bowl, whisk buttermilk, oil, eggs, and vanilla until smooth. Pour into dry ingredients and mix until just combined. Slowly stir in hot coffee until batter is smooth and thin.
Divide batter evenly among prepared pans. Bake for 25-30 minutes, until a toothpick inserted in center comes out with a few moist crumbs. Cool in pans for 10 minutes, then turn out onto wire racks to cool completely.
While cakes cool, melt butter in a large skillet over medium heat. Add chopped kunafa and cook, stirring frequently, for 8-10 minutes until golden brown and crisp. Spread on a plate to cool completely.
In a heatproof bowl, combine white chocolate chips and 2 tablespoons of the heavy cream. Microwave in 20-second bursts, stirring until smooth. Stir in pistachio paste until fully incorporated, then fold in cooled kunafa.
Place one cake layer on a serving plate. Spread half of the pistachio filling evenly over the top, leaving a small border. Top with second cake layer and remaining filling. Place final cake layer on top, pressing gently to level.
Place chopped dark chocolate in a heatproof bowl. Heat remaining heavy cream until just simmering, then pour over chocolate. Let sit for 2 minutes, then stir until smooth and glossy. Let cool for 10-15 minutes until slightly thickened but still pourable.
Pour ganache over the top of the cake, letting it drip down the sides. Use an offset spatula to smooth the top and spread drips. While ganache is still tacky, press finely crushed raw pistachios onto the sides of the cake.
Refrigerate cake for at least 6 hours, preferably overnight, to set filling and ganache. Before serving, garnish with toasted whole pistachios. Let cake sit at room temperature for 20-30 minutes before slicing.