Preheat your oven to 350°F (175°C). Grease two 9-inch cake pans, line the bottoms with parchment paper, and lightly dust them with cocoa powder or flour.

In a large bowl, sift together the flour, cocoa powder, baking powder, baking soda, and salt. Stir everything well so the dry ingredients are evenly mixed.

In another bowl, beat the eggs and sugar until the mixture becomes lighter in color. Mix in the vegetable oil, vanilla extract, and buttermilk until smooth.

Gradually add the dry ingredients into the wet mixture, stirring gently until just combined. Slowly pour in the boiling water while mixing. The batter will be thin, which helps create a moist cake.

Divide the batter evenly between the prepared cake pans. Bake for 30–35 minutes or until a toothpick inserted into the center comes out clean. Let the cakes cool in the pans for 10 minutes before transferring them to a wire rack to cool completely.

To prepare the frosting, place the egg whites and superfine sugar over a saucepan of gently simmering water. Whisk continuously until the sugar completely dissolves and the mixture feels smooth.

Transfer the warm egg white mixture to a mixing bowl and beat until thick, glossy peaks form and the bowl feels cool. Add the softened butter one tablespoon at a time, beating well after each addition. Finally, pour in the melted dark chocolate and mix until the frosting is silky and smooth.

Place one cake layer on a serving plate and spread a generous layer of frosting over the top. Add the second cake layer, then frost the top and sides evenly. Decorate with dark chocolate flakes and allow the cake to rest for about 20 minutes before slicing and serving.