Instructions

1. Chocolate cake
   Preheat the oven to 180 C (350 F) standard / 160 C (320 F) fan-forced. Grease and line three 8-inch round cake pans with baking or parchment paper.
2. In a large mixing bowl, sift the flour, cocoa powder, baking powder and baking soda. Then add the sugars. Whisk together. In a separate mixing bowl, add the buttermilk, vegetable oil, vanilla, eggs and sour cream. Whisk together. Boil the kettle and pour out 1 cup of hot water.
3. Add the wet ingredients to the dry ingredients. Start to fold together, slowly pour in the hot water, and continue to mix until all the ingredients are incorporated. Divide the mixture evenly into three cake tins and bake for approximately 25-30 minutes or until a skewer inserted comes out clean. Leave for 10 minutes before gently removing the cakes from their tins and leave them to cool completely on a wire rack.
4. Chocolate crumbs
   Next, make your chocolate crumbs. In a large mixing bowl, add your plain flour, sugar, cornflour and cocoa powder. Whisk together. Melt your butter and add it to the mixture, stirring until it forms wet crumbs. Pour this mixture out onto a baking tray lined with baking paper and spread out into one layer. Bake for 10 minutes, then leave to cool completely.
5. Chocolate frosting
   To make the frosting, place your softened butter in a large mixing bowl and beat with an electric mixer on medium speed for a couple of minutes until pale and creamy. Meanwhile melt the chocolate in a microwave, stirring in between 20 second bursts, until just melted and set aside to cool a little.
6. Once the butter is very pale and creamy, add one cup of icing sugar and one tablespoon of milk and beat on low until the sugar is incorporated and then beat on medium speed until combined. Next, add the rest of the sugar, one cup at a time, and the milk, one tablespoon at a time, until thick and creamy.
7. Next, add your melted chocolate to the buttercream mixture, ensuring the chocolate is still smooth and melted but is not warm. Beat until the chocolate is completely mixed through.
8. Milk chocolate ganache
   To make the chocolate ganache, roughly chop the milk chocolate and add to a small bowl. Pour over the cream and the pop in the microwave for 20 second bursts, stirring in between, until chocolate has melted. Put the ganache in the fridge for about 15 minutes to thicken.
9. Chocolate soak
   To make the chocolate soak, stir together milk and chocolate powder.
10. To assemble cake
    Level the tops of your cakes using a cake leveler or a serrated knife. Set the leftover cake to the side. Place one of your cakes onto a turntable, if you have one, then gently brush the top of the cake with the chocolate soak. Add chocolate frosting and spread to the edges. Cover in chocolate cookie crumbs and then drizzle with milk chocolate ganache.
11. Add second cake layer on top. Then repeat with chocolate soak, chocolate frosting, cookie crumbs and chocolate ganache. Add the final layer of cake on top. Then cover the entire cake with chocolate frosting. Use a cake scraper to remove excess chocolate frosting. Add the remaining cookie crumbs and chocolate ganache on top. Cut and serve