Heat the oven to 200C/180C fan/ gas 6. Butter the base and sides of two 20cm cake tins (4cm deep) and line with baking parchment. Put the butter and sugar in a stand mixer fitted with the whisk attachment and beat for 2-3 mins until pale, light and fluffy. Alternatively, do this in a bowl using an electric whisk. Add the eggs one at a time, beating well between each addition until fully incorporated.

Mix the cocoa powder, vanilla extract and red food colouring gel together in a small bowl or jug with 2-3 tbsp hot water until you have a smooth, lump-free paste. Tip this into the bowl with the cake batter and whisk briefly to combine.

Mix the vinegar and buttermilk together in a jug. Combine the flour, bicarb and 1 tsp salt in a bowl. Pour a third of the buttermilk mixture into the cake batter, then mix in along with a third of the flour mixture until fully incorporated. Alternate between the remaining buttermilk and flour mixtures, mixing these in a third at a time until everything is fully combined, being careful not to overmix.

Divide the cake batter equally between the prepared tins and bake for 30-35 mins until the sponges spring back when gently pressed with a fingertip and a skewer inserted into the centre of each comes out clean. Do not open the oven before 25 mins have elapsed, as this can cause the sponges to sink in the centre. Leave to cool in the tins for 5 mins, then turn out onto wire racks to cool completely.

To make the buttercream, clean out the bowl of the stand mixer, then tip in the butter and vanilla bean paste (or do this in a bowl using an electric whisk). Beat on high speed for about 1 min until creamy and smooth. Gradually add the icing sugar, about a quarter at a time, beating between each addition on a low speed until just incorporated. When all the icing sugar has been added, turn the speed up to high and beat for 1 min. Turn the speed back down to low, then tip in the soft cheese and beat until just combined and smooth.

Split both of the cooled sponges through the middle using a cake leveller or large bread knife so you have four equally sized, thin layers. Spread a little buttercream over the middle of a 20cm round cake board and top with a sponge layer. Spread buttercream generously over the top of the sponge layer so it sticks out over the edge slightly. Top with a second sponge layer and repeat until you’ve used all the sponges, inverting the final sponge layer so that the top is flat. Spread any buttercream that’s sticking out from between the sponge layers all around the side of the cake using a palette knife to seal the stack.

Next, spread a thin, even layer of buttercream over the whole cake down to the cake board to seal it completely. Once you have covered the whole cake, clean the palette knife and go around the cake again to smooth the sides and remove any excess. This is called a crumb coat, which seals in any crumbs and will make the finished cake look neater. Chill the cake for at least 30 mins until firm and set.

Spoon 300g of the remaining buttercream into a bowl and keep chilled to pipe with later. Spoon the rest of the buttercream over the top of the chilled cake (reserving a little to secure the cake to a cake stand), then use a palette knife to spread it to the edge and encourage it to drop slightly over the side. Then, hold the palette knife vertically against the side of the cake and smooth over the buttercream, turning the cake as you go so the side is covered in a thick, even layer (a cake turntable can help with this, if you have one, or see our tip, right). Once you’ve covered the side, you may wish to clean the palette knife and smooth the top and side again to ensure the buttercream is neat, or do this with a side scraper if you have one. Transfer the cake, on its board, to a cake stand using the reserved buttercream to secure it in place.

Place the cake, on its stand, on a baking tray (this will catch any excess sprinkles). Press most of the sprinkles around the bottom third of the cake in a thick band, sticking a few up the side in places so it looks as though some have floated away from the band. Use a cutlery or palette knife to gently press the sprinkles into the cake to ensure they’re secure, then carefully brush any excess from the stand using a pastry brush. Chill for 30 mins.

Meanwhile, prepare the shimmering chocolate truffles, if using. Tip a few teaspoons of gold lustre dust into a small bowl, then do the same with the pink lustre dust in another bowl. Divide the chocolate truffles between the two bowls and turn with your fingertips or a teaspoon until fully coated in the lustre dust. Set aside on kitchen paper.

When the cake is chilled and set, stir the 300g reserved buttercream with a spoon to soften and remove any air bubbles. Spoon into a piping bag fitted with a large star nozzle, then pipe a thick, swirled border around the top of the cake (this doesn’t need to be exact), then scatter the remaining few sprinkles all over the top of the cake and nestle the shimmering truffles in amongst the piped rosettes. Will keep in the fridge for three days.