Instructions for the cake

• Preheat oven to 180 degrees Celsius and grease and line 1-2 deep cake tins.
• Pour milk, water and vinegar into a large jug and set aside for 10 minutes.
• In a large bowl, combine flour, sugar, cocoa and baking powder.
• Pour milk mixture, vanilla and dye (a little bit at a time, adding more until it's the colour you want), and carefully mix with a spatula until just combined.
• Pour mixture into prepared cake tins and lightly hit them against your kitchen counter to remove air bubbles.
• Bake for approximately 1 1/2 hour or until cakes spring back when touched.
• Set cakes aside to cool completely.

Instructions for the buttercream and decorations

• Place aquafaba into a stand mixer fitted with a whisk attachment, and start beating on a medium setting.
• Place sugar into a saucepan and heat until it reaches 110 degrees Celsius.
• Slowly pour sugar syrup into whipped aquafaba, and increase speed. Beat for a further 2 minutes.
• Turn off mixer and change from a whisk attachment to a paddle attachment. Place the meringue into the fridge to cool completely. If you add the butter whilst it's still hot, the butter will melt and you'll end up with a liquid mixture. 
• Add 1/5 of the butter and start beating icing again, slowly adding more butter once it is incorporated. 
• Add flavouring and beat for a further 10 minutes.
• Once cool, divide cake into 3 equal layers (or cut your 2 cakes in half to make 4 layers) and place the middle layer onto a cake board of the same size, using some buttercream to secure it into place. Put that cake board onto a larger cake board.
• Place cake onto a turntable (you may need to place the turntable onto something to increase its height so it's close to chin level).
• Ice the top of each layer, making sure to put what was originally the bottom of the cake on top, as this will have the smoothest surface.
• Using a spatula, complete a crumb layer of the cake and place in the fridge to set for 1 hour. The crumb layer is designed to trap all of the crumbs that appear once you start icing, so don't worry if the cake looks messy at this stage, and don't use too much icing. It's okay to see the cake under the icing. 
• Divide remaining icing into 3 bowls and colour each bowl with a different food dye, so you end up with 3 different colours. 
• Fill 3 icing bags fitted with large, round piping tips with the icing.
• Using toothpicks, divide the cake into 3 layers. These will help you icing the cake evenly.
• Hold the first icing bag against the cake on an angle towards yourself, carefully squeeze out icing with one hand and rotate the turntable with the other. Repeat with all 3 layers, and don't worry if it's still messy as you will be cleaning it up shortly!
• Take a clean, straight cake scraper that is long enough to reach the top of your cake when standing on the cake board, and stand it against your cake on a slight angle towards you. Rotate the turntable to smooth the icing, removing excess icing from the cake scraper as you go.
• Use a small spatula to fill in any holes and keep scraping until it is as smooth as you can get it. 
• Place the cake back into the fridge to set for a further 30 minutes.

Instructions for the ganache

• Warm milk and teabags in a small saucepan over a low heat, until it starts to bubble but before it starts to boil. Turn off heat but leave saucepan on the stove top with teabags to brew for 10 minutes.
• Remove teabags and reheat milk on a low heat, slowly adding pieces of chocolate and stirring constantly. 
• Turn off heat after all chocolate has been addded and keep stirring until mixture is smooth and well combined. Leave to cool slightly. 
• Spread ganche over the top of the cake and let it drip down the sides, adding some shortening or oil to the mixture if it's too thick to drip.
• Place remaining icing (I only had 2 colours left at this stage) into a larger piping bag and decorate the top of the cake. 
• Decorate the sides and top with sprinkles and edible glitter and place in the fridge until 1 hour before serving.