Preheat your oven to 350 °F (175 °C).

In a large bowl, mix sugar, flour, cocoa powder, baking powder, cinnamon, and salt with a whisk.

Add olive oil, milk, vanilla, and egg; whisk until smooth.

Pour the batter into an 8-inch round cake pan that is greased, floured, and lined with parchment paper. Bake for 37-40 minutes until a toothpick inserted in the middle comes out clean or with a few crumbs.

Chop the kataifi pastry and fluff it up with your hands to separate strands.

In a large pot over medium heat, add the butter and kataifi pastry. Stir often using two forks to keep strands fluffy. Toast until deep golden brown, then transfer to a bowl to cool completely.

Melt the white chocolate (and vegetable oil if using) in a bowl, add pistachio butter and salt; mix well and let cool until slightly thickened.

Add the cooled toasted kataifi pastry to the pistachio cream and mix well.

Whip the cold heavy cream with a hand mixer until soft peaks form. Add honey and combine, then add melted dark chocolate and quickly mix until homogenized. Keep in the fridge until needed.

The next day, take the ganache out of the fridge to warm slightly. Trim the dome of the chocolate cake and cut it into two layers.

Place one cake layer onto a cake platter, pipe a border with the ganache, and fill with the pistachio and kataifi filling.

Cover with the second cake layer and frost with remaining whipped chocolate ganache.

Dip an offset spatula in hot water to smooth the surface of the cake, then sprinkle chopped pistachios on top for decoration.