This cake will take 2 days to make, as the jam, aquafaba syrup and the sponge itself will need to be cooled overnight in the fridge.
Blueberry Jam Ingredients
Blueberries – 350g
Sugar – 150g
Lemon – 1/8 (this is optional, it is needed for the jam to “gel” as blueberries are low in pectin)
Blueberry Jam Instructions
Wash the blueberries, and put into a saucepan with the sugar and lemon. Start the jam off on a low heat until the sugar has melted, then increase the heat to boil the jam, and cook until it reaches 105 C. Once ready, pour into a container and leave to cool overnight.
DF Swiss “Buttercream” Ingredients
Aquafaba (water from a jar of chickpeas) – 300ml (about 2 cans)
Sugar – 150g
Cream of tartar – 1/2tsp
Vegetable shortening (100%fat) – 500g
Vanilla extract – 1tbsp
Lemon extract – 2tsp (don’t use lemon zest, it will clog the piping nozzle tips)
DF Swiss “Buttercream” Instructions
Mix the aquafaba with the sugar in a saucepan, and boil on the stove for 5 minutes. Leave to cool overnight in the fridge.
The next day, take the aquafaba syrup and the vegetable shortening out of the fridge and leave at room temperature for 1 hour.
Whisk the aquafaba syrup in a stand mixer. When it starts to foam add the 1/2tsp of cream of tartar.
Once the aquafaba has reached “stiff peaks” start adding the vegetable shortening 1tbsp at a time. At this point, the cream is at risk of splitting, if this happenes, keep whisking, it will eventually come back together.
Add the vanilla and lemon extracts at the very end once the cream has come together.
Lemon Sponge Cake Ingredients
You will need 2 batches of this cake mixture. The quantities listed below are for 1 batch.
Eggs – 6
Sugar – 150g
Lemon zest – 1 lemon
Flour (plain flour, or GF bread flour) – 180g
Lemon Sponge Cake Instructions
Preheat oven to 150 C Fan. Use a 20x30cm square baking tin. If you only have 1 cake tin, make and bake 1 batch of the cake mixture at a time.
In a stand mixer, whisk the eggs until frothy, then gradually add the sugar. Continue whisking until the eggs are pale and have reached the “ribbon stage”. Add in the lemon zest.
Sift and fold in the flour into the eggs.
Bake for 40-50 minutes.
Wrap in clingfilm, and put into the fridge overnight.
Assembley and Decoration
- Sugar Syryp – a few tablespoons.
- Yellow gel food colouring.
- Petal tip #81 – for 3 yellow chrysanthemum flowers.
- Writing tip #3 – for yellow flower stems and birthday message.
- Mint leaves – 8 leaves of various sizes.
- Tiny blueberries – about 17.
- Star tip #21 – for 2 yellow shell borders, 1 at the base, 1 around the top.
To assemble the cake, slice the 2 layers in half, which will result in a total of 4 cake layers. Follow the assembley using the diagram below. As you stack the sponge, drizzle each layer with a few tbsp of sugar syrup – this will keep it moist. Make sure to use the minimum amount of Swiss “Buttercream”, so that there is enough left over to coat the whole cake, and also to colour yellow and decorate the top of the cake.
Once the cake is assembled, cover the whole cake with a crumb coat, and then the final “buttercream” coat. Put into the fridge to chill.
Colour the remaining Swiss “buttercream” with the yellow gel colouring.
Make 3 chrysanthemum flowers using the petal tip #81, in 3 different sizes, put these into the freezer to firm up – this makes it easier to transfer onto the cake later.
Take the cake out of the fridge, and use a toothpick to lightly mark out the stems and the birthday message. Then use the writing tip #3 to pipe in the lines.
Add the blueberries and mint leaves, then place the chrysanthemum flowers. Now pipe the 2 shell borders using tim #21. The giant birthday cake is now complete!