Preheat oven to 350°F (175°C). Grease and flour two 8-inch round cake pans. Line bottoms with parchment paper.

In a large bowl, whisk together flour, sugar, cocoa powder, baking powder, baking soda, and salt.

In another bowl, whisk together eggs, milk, vegetable oil, and vanilla extract.

Pour wet ingredients into dry ingredients. Mix until just combined.

Carefully whisk in hot water until combined. Batter will be thin.

Divide batter evenly between prepared pans. Tap pans gently.

Bake 27-32 minutes, or until a skewer comes out clean.

Cool cakes in pans on wire rack for 10-15 minutes. Turn cakes onto wire rack to cool completely.

If using kataifi, cook in melted butter until golden and crispy. If using phyllo, bake until crispy and break apart. Cool completely.

In a bowl, mix pistachio cream with cooled crispy pastry pieces. Add powdered sugar or tahini if desired.

Make chocolate ganache by heating heavy cream and pouring over chopped chocolate. Let sit 5 minutes, then stir until smooth.

Place one cake layer on a plate. Spread pistachio filling over it. Top with second cake layer.

Spread chocolate ganache over top and sides of cake.

Garnish with chopped pistachios if desired.