Preheat your oven to 350°F (175°C). Grease and line two 8-inch round cake pans, or line a 12-hole muffin tin with paper liners if making cupcakes.

In a large mixing bowl, whisk together the flour, granulated sugar, cocoa powder, baking soda, and salt until evenly distributed.

Add the buttermilk, vegetable oil, eggs, and vanilla extract to the dry ingredients. Whisk gently until a smooth batter forms, being careful not to overmix.

Divide the batter evenly between the prepared cake pans (or fill cupcake liners 2/3 full). Bake for 30-35 minutes for cakes, or 18-20 minutes for cupcakes, until a toothpick inserted in the center comes out clean.

While the cakes are baking, prepare the crunchy kunafa filling. In a large skillet over medium heat, toss the chopped kataifi dough with the melted butter. Toast for 5-7 minutes, stirring constantly, until deeply golden brown and crispy, then remove from heat to cool.

In a separate chilled bowl, use an electric mixer to whip the heavy cream until soft peaks form. Gently fold in half of the sweet pistachio cream until you achieve a light, fluffy pistachio mousse.

Once the cakes or cupcakes have cooled completely, spread the remaining pure pistachio cream over the bottom cake layer (or core and fill the center of the cupcakes). Sprinkle a generous layer of the cooled, crispy kunafa over the pistachio cream.

Place the second cake layer on top (if making a cake) and frost the outside with the whipped pistachio mousse. Garnish the top with the chopped toasted pistachios and any leftover crispy kunafa right before serving to maintain maximum crunch.