• Preheat the oven to 170oC/150oC fan and grease and line two 20cm springform cake !ns with parchment paper.
• In a large bowl, cream the butter and sugar together until light and fluffy. Add the flour, cocoa powder, eggs and vanilla extract and beat again until well combined.
• Divide the mixture between the two !ns and bake in the oven for 50–60 minutes, or until a cocktail stick or skewer inserted into the middle of the cakes comes out clean. Leave to cool in the tins for 10 minutes, then turn out onto a wire rack and leave to cool fully.

Buttercream

• In a large bowl, beat the butter to loosen it. Add the icing sugar and cocoa powder and beat well until smooth and fluffy.
• Gradually pour in the double cream, beating continuously until smooth.
• Split the two cakes into four layers by slicing each cake in half horizontally, using a long serrated knife.
• Put the first cake layer onto a cake board or a flat plate. Using a palette knife, add two tablespoons of buttercream and spread over the top of the layer.
• Stack and repeat with the second and third sponge layers. Add the final sponge layer on top.
• Using the remaining buttercream, spread and smooth a thin layer around the cake sides and top for a crumb coat and chill in the fridge for at least 30 minutes.

Ganache

• Break the dark chocolate and milk chocolate into equal pieces andput in a heatproof bowl. Heat the double cream in a small pan until just before boiling point. Pour the hot cream over the chocolate and leave to sit for at least 5 minutes.
• Stir to combine until smooth.
• If lumps of chocolate still remain, put the mixture back into the pan over a low heat and stir until smooth, or microwave briefly.
• Let the ganache cool slightly in the bowl, stirring every few minutes until it forms a peanut-butter-like consistency. The cooling process can be sped up by placing the bowl in the fridge, but be sure to stir it frequently, so it doesn’t set too quickly.
• Once the ganache has set slightly, it can also be whisked with a hand-held electric whisk to give it a lighter and more mousse-like texture.
• Remove the chilled cake from the fridge and use a small angled spatula to smooth the ganache over the top and sides of the cake.
• I use a large metal scraper to achieve an even finish.
• Return the cake to chill in the fridge again for at least 30 minutes.

Ganache Drip Decoration

• Break the dark and milk chocolate into equal pieces and add to a heatproof bowl with the double cream. Microwave in short bursts until smooth.
• Transfer the mix to a small piping bag or use a teaspoon to drip the ganache down the sides of the cake. The more ganache you push over the edge, the further the drip will fall.
• Return the cake to chill in the fridge again for 30 minutes.
• Finally, decorate the cake by piping over any leftover ganache or buttercream in swirls, scattering over sprinkles and adding truffles if desired.