Heat the oven to 180C/160C fan/gas 4. Oil three 20cm cake tins and line with baking parchment. Weigh out the flour, cocoa powder, baking powder, bicarb and sugar into a large bowl, add a pinch of salt and whisk gently to combine. Shake the bowl to bring any lumps of sugar to the surface and squeeze these with your fingertips.

Measure the oil, milk, vinegar, coffee and vanilla into a jug, then add the eggs and whisk to combine. Pour the wet ingredients into the dry and stir with a whisk until smooth, making sure there are no pockets of flour at the bottom of the bowl – the mixture will be quite runny. Divide the batter evenly between the prepared tins, then bake on the middle shelf of the oven (or middle and top if they don’t all fit on one shelf) for 25 mins. Swap the tins around and bake 5 mins more.

Check the cakes are cooked by inserting a skewer into the centre of each – if any wet batter clings to the skewer, return the tins to the oven for another 5 mins, then check again. Leave to cool in the tins for 30 mins, then turn the sponges out onto wire racks to cool completely. If making ahead, wrap the cooled sponges well and store in an airtight container for up to three days, or the freezer for up to two months.

For the buttercream, beat the butter using an electric whisk or in a stand mixer for a few minutes until smooth and creamy. Add half the icing sugar and beat again to combine. Add the remaining icing sugar, the vanilla and 4 tbsp milk and beat again to combine, adding a splash more milk if needed to make a smooth, fluffy buttercream. Divide between three bowls. Add a few drops of different food colouring paste to each bowl, then mix well – we used pastel pink, purple and yellow.

Spoon the coloured buttercream mixtures into three separate piping bags and snip off the tips. Pipe a dot of buttercream onto a cake stand or board and place a sponge on top to help keep it in place. Pipe small blobs of purple buttercream all over the top of the sponge by holding the piping bag directly above the cake, about 1/2cm from the surface, and squeezing the bag while pulling upwards to create a small peak.

Place the second sponge on top, then repeat the process with the pink buttercream. Add the third sponge on top, then neatly pipe blobs of yellow buttercream over the surface. Decorate with edible flowers, sugared almonds or mini chocolate eggs, if you like. Will keep in a tin at room temperature for up to five days.