Preheat oven to 350°F and prepare two 8 inch cake pans
Sift all the dry ingredients for the cake into a large bowl and stir together
Add the eggs, oil, milk and vanilla and mix everything together until it is combined and there are no lumps
Add the hot water and continue to mix until totally incorporated
Pour evenly into cake pans and tap the pans on the counter a few times to release any large air bubbles
Bake for 30-40 minutes, or until a skewer comes out clean
Make the Chocolate Ganache
Chop the chocolate into small pieces and put into a bowl
Heat the cream in a saucepan over a medium-low heat until just before boiling, remove from the heat and pour over the chopped chocolate
Stir the chocolate and cream together until all the chocolate has melted and the mixture is thick and glossy. Allow to cool before using
Make the Chocolate Buttercream
Cream butter until smooth
Add cocoa powder and beat together
Add icing sugar, milk and vanilla and beat on high for 3 minutes until frosting is creamy
Assemble and Decorate
Cut the domes off of the two chocolate sponges so they have flat tops
Cut each cake in half
Place one of the cake layers down on a plate or cake board and spread with chocolate buttercream, add another layer on top followed by more buttercream
Before adding a third cake layer, pour some of the chocolate ganache on top of the buttercream and spread to the sides (don't add too much or the cake will be slippy. Add the third cake layer on top, followed by more buttercream and the final cake layer
Once the cake is stacked, cover the whole thing in chocolate buttercream and either smooth it out. Put the cake in the fridge to chill for 15 minutes
Once the cake has chilled, heat the chocolate ganache in the microwave for 5 seconds, just to soften it up a little, put it in a piping bag and cut a small piece off the tip
Use the piping bag to pipe drips of ganache down the side of the cake, all the way around. Once you have all your drips, use the remaining ganache to cover the top of the cake, smooth it out and place it back in the fridge for 5 minutes
Take any remaining chocolate buttercream and put it into a piping bag with a star nozzle, pipe rosettes on top of the cake and finish with some chocolate sprinkles
Notes
Cut the two cake layers in half length ways to make 4 layers total, and frost in between each layer with the chocolate frosting. Then coat with the chocolate ganache.