For the chocolate cake layers:

1. In a bowl, whisk together hot water and cocoa powder until the cocoa has dissolved. Set aside to come to room temperature.
2. In a mixer with a beater attachment, mix butter with sugar on medium speed until pale and creamy, about two minutes. Scrape down to the bottom of the bowl once during mixing to make sure no butter is stuck at the bottom.
3. Add eggs one at a time, mixing on the lowest speed after each addition until incorporated, about 30 seconds.
4. Add vanilla and mix on lowest speed for about 30 seconds to combine.
5. In a bowl sift flour, baking soda, baking powder and salt. Add a third of the flour mixture to the mixing bowl and mix on lowest speed to incorporate.
6. Add half of the cocoa mixture to the mixing bowl and mix on lowest speed to incorporate. Repeat with another third of the flour mixture, then the remaining cocoa powder mixture, and then the remaining flour mixture. Mix just until the ingredients are combined.
7. Grease the inside (base and sides) of three 8" pans with non-stick spray, butter or oil. Divide batter between the cake pans.
8. Bake at 175ºC or 350ºF for 35 minutes, or until a toothpick inserted into the middle of the cake comes out clean.
9. Let cakes cool in their pans for 10 minutes. Use a spatula to loosen cake from the edges of the cake pan and then turn onto a wire cooling rack. Leave to cool completely.

For the chocolate kataifi:

1. Melt the chocolate chips in the microwave for 1 minute at 60% power. Stir and repeat until smooth.
2. Pour the kataifi into a bowl. Drizzle melted chocolate on top and then stir together with a fork to coat the kataifi in chocolate. Transfer to a tray lined with parchment, wax paper, or a silicone mat and leave to cool.

For the chocolate ganache:

1. Pour the chocolate chips into a bowl.
2. Heat the cream in a bowl in the microwave for 30 seconds or in a pan over medium heat until bubbles appear around the edges of the pan.
3. Pour the cream over the chocolate chips and use a spoon to push all of the chocolate chips below the surface of the cream. Leave for 5 minutes and this stir until smooth. Set aside to cool.

For the pistachio buttercream:

1. In a food processor, blend pistachios until coarsely chopped. Remove 1/2 a cup and set aside to decorate the cake later. Blend the remaining pistachios until fine. Add water and continue blending to make a paste.
2. In a mixer or using a handheld mixer, beat butter at low speed for a minute until smooth.
3. Add pistachio paste and mix in until combined.
4. Sift sugar to remove any lumps and then add with salt to the mixing bowl and mix at low speed until combined. Scrape down to the bottom of the mixing bowl to loosen any ingredients stuck there.
5. Add milk to loosen the buttercream. It should be smooth and easy to stir.

To put it all together:

1. Spread some buttercream or ganache onto the middle of a cake board and press the first chocolate cake layer onto it to attach it. Spread a layer of ganache on top, then sprinkle chocolate kataifi over it, and spread pistachio buttercream on top.
2. Place the next chocolate cake layer on top and repeat the fillings, finishing iwht the final cake layer.
3. Chill the cake in the fridge for 30 minutes or in the freezer for 10 minutes before continuing. This firms up the cake so it's easier to frost.
4. Cover the cake with half of the remaining pistachio buttercream as a crumb coat. Smooth it to flatten any bumps and bulges but don't worry about making it perfect.
5. Put the cake back in the fridge or freezer for 30 minutes to set the crumb coat. Meanwhile, make the chocolate truffles by following the steps below.
6. Spread the rest of the pistachio buttercream onto the cake and smooth it.
7. Place the cake on a tray and press the crushed pistachios around the bottom of the cake. They'll stick because the pistachio buttercream frosting is still soft and sticky. The tray will catch any pistachios that fall off the cake board.

For the chocolate truffles:

1. Use a spoon to scoop up the chilled ganache and sprinkle some chocolate kataifi on top. Roll it between your hands (I wore gloves for this because it's messy!) to make a ball and then roll it in the cocoa powder.
2. Place the truffles on top of the cake. I made 10 but recommend at least 12 to mark out individual portions, since cutting this cake into only 10 slices made HUGE portions!