
This stunning triple-layer cake features moist chocolate sponges infused with a hint of coffee, topped with vibrant, multi-colored vanilla buttercream. Perfect for birthdays or special occasions, it's as beautiful to look at as it is delicious to eat.
Preheat your oven to 180°C (160°C fan/gas 4). Lightly grease three 20cm cake tins with oil and line the bases with baking parchment. In a large mixing bowl, whisk together the flour, cocoa powder, baking powder, bicarbonate of soda, and sugar with a pinch of salt. Shake the bowl to bring any sugar lumps to the surface and break them up with your fingertips.
In a large jug, whisk together the vegetable oil, milk, vinegar, cooled coffee, vanilla, and eggs until well combined. Pour the wet ingredients into the dry mixture and whisk until smooth, ensuring no flour pockets remain at the bottom. The batter will be quite thin and runny.
Divide the batter evenly between the three prepared tins. Bake on the middle shelf for 25 minutes, then swap the tins around and bake for an additional 5 minutes. Test with a skewer; if it comes out clean, the cakes are done. Let them cool in the tins for 30 minutes before transferring to a wire rack to cool completely.
To make the buttercream, beat the softened butter with an electric whisk or stand mixer for several minutes until very pale and creamy. Add half of the icing sugar and beat again. Incorporate the remaining icing sugar, vanilla, and 4 tablespoons of milk. Whisk until fluffy, adding a splash more milk if the consistency is too stiff. Divide the frosting into three separate bowls.
Tint each bowl of buttercream with a few drops of different food coloring pastes (such as pastel pink, purple, and yellow) and mix well. Transfer each color into a separate piping bag and snip off the tips. Secure the first sponge onto a cake stand with a small dot of buttercream. Pipe small peaks of the purple buttercream across the entire surface of the sponge by squeezing the bag and pulling upward.
Place the second sponge on top and repeat the piping process using the pink buttercream. Add the final sponge and pipe neat yellow buttercream peaks over the top. Decorate with edible flowers, sugared almonds, or mini chocolate eggs if desired. The cake will stay fresh in an airtight container at room temperature for up to five days.
For the most vibrant colors, use gel or paste food coloring rather than liquid, as liquid can thin out the buttercream. If you are making this ahead of time, the sponges can be frozen for up to two months—just wrap them tightly in plastic wrap once completely cooled.