Pre-heat your oven to 180°C/ 356°F. Prep two baking trays with baking paper on the bottom. I used 2 deep 6-inch baking trays for this recipe (which I then cut into 4 slices). If you use 8-inch baking trays, you will be able to do two normal layers.
In a large bowl, combine the milk and the apple cider vinegar. Put this to the side and allow it to curdle for a couple of minutes. Then add the oil, sugar and vanilla extract to the milk mixture. In another bowl, sieve the flour, cocoa, salt, baking powder + soda and combine. Using a large spoon, add the dry mixture to the wet, whisking as you go.
Pour your cake batter into the two baking trays and bake for 50 minutes, or until a toothpick comes out clean. Leave to cool. If you make 8-inch cakes you only need to bake for 30 minutes.
Once your cakes are completely cool, cut the top off of them to ensure that they are completely flush with the baking tray. This means they are both equal heights. Then, cut them into equal layers. I did four cake layers and I used a cake leveller to do this.
In a standing mixer, mix the butter on a high speed for around 5 minutes. This will cream the butter. Then, add the icing sugar, Raspberry extract + Pink flavouring. Mix on a low speed for around 30 seconds and then increase to a high speed, until combined and fluffy (around 3 minutes). Add a tablespoon of water if you need to loosen the icing up a bit or more icing sugar if you want it thicker.
Using a cake plate, layer the sponges up evenly with the raspberry buttercream icing in the middle. Scatter some fresh raspberries on top of the icing in the layers, before you add the next cake layer. This is optional but will add a yummy fresh fruit addition. Then add the remaining buttercream to the outside of the cake. I use a cake spatula to make this smooth. Add any decoration that you wish to the top - I used buttercream swirls and fresh raspberries! Enjoy :D