the rainbow mermaid layer cake


I think this cake speaks for itself.

Perhaps it’s the fact each of the layers of this one was a different, garish colour – or maybe the marvellous consistency of cake drips down the sides, but this cake was pretty much the ultimate statement to myself that I can produce something both genuinely beautiful and very, very edible. I’ve undeniably drawn inspiration from the incredible Sweetapolita and Katherine Sabbath, but the satisfaction of creating this was utterly all my own.

I’m feeling much more confident with the technique of assembling layer cakes neatly (cling wrap and freeze the cakes, crumb coat, secure the cake to the stand with a blob of frosting, thank me later). This cake, however, involved two new experiments: 1) cooking meringues using Ottolenghi’s method and 2) Swiss meringue buttercream. I’ve never played with either of them, and they both played roles in the huge success of this cake. This cake could just as easily be iced with regular buttercream, but spreading my wings into the SMB territory means I have much more flexibility with a smoother, richer and less cloyingly sweet frosting to play with. I would not do it without a sugar thermometer, however if you have one on hand (and you should, do I need to write a fudge recipe to convince you?), it’s pretty much paint by numbers.

Bizarrely, the person who told me it was “the best cake he’d eaten all year” (easy to achieve I suppose, though we are already halfway through April), also suggested that my cake could have perhaps been created to celebrate Rastafarianism. I was really trying for mermaid meringue dreaminess, but I suppose I left it rather open to interpretation.

Once again, “where do you have the time?” came into play with this cake (I brought it to work for a birthday). It took, at most, four hours of dedicated time in the kitchen (excluding time for cooling cakes, baking, etc). For me, to produce such a pretty final product whilst learning new cooking techniques is something I’m always going to find time for. It’s how I relax, but it’s also how I feel fulfilled.

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Making the cake can be easily spread over an entire week of preparation:

  • Meringues – can be stored in an airtight container for up to 1 month
  • Cakes – store in cling film in the freezer for up to 1 month
  • Decorations – sprinkles and M&M’s can be easily purchased way in advance
  • Swiss meringue buttercream – can allegedly be froze and refrigerated, but my first prepped in advance batch was not revived to its original fluffiness, so personally I would prepare this on the day
  • Candy melt ganache – on the day

I purchased liquid egg whites for this occasion, and despite the obvious convenience, I really have to wonder where all the yolks go.

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Let’s go!

Meringues (makes ~30 small piped meringues), thank you Ottolenghi:

  • 60g egg whites (or two free range egg whites), room temperature
  • 120g caster sugar
  1. Heat the oven to 200C, bake. Spread the sugar out evenly across a baking try lined with parchment and “bake” until the edges are just starting to melt. This takes about 8 minutes and takes near constant vigilance!
  2. Wipe the inside of your mixing bowl, and the whisk, with the cut side of the lemon to remove any grease and add the egg whites. As soon as you spot the sugar beginning to melt at the edges, set the mixer to whisk at high speed while you take the sugar out of the oven.
  3. The mixture should be just foamy by the time you add the sugar. Wearing oven gloves, pick up the baking parchment with oven gloves and pour the hot sugar into the egg whites while continuing to beat (this is quite the feat if using a hand-beater, as I did, I will have you know). Continue whisking until the mixture has cooled, and is glossy and will hold its shape. Turn the oven down to 100C bake setting.
  4. Using a piping bag (I alternated between a 1M Wilton tip and a plain circle for my stars and “puffs”), pipe your desired shape and size of meringues onto a baking sheet lined with silpat or parchment. Try to keep them reasonably evenly in size, bearing in mind that obviously the smaller ones will cook first.
  5. Bake for 2-3 hours (I’ve given leeway to allow for taste testing opportunities aplenty) until fully cooked through. Remove from the oven, cool and store in an airtight container in a cool place.

For the rainbow vanilla cake (I adapted Nigella’s buttermilk birthday cake):

  • 170g softened butter
  • 270g caster sugar
  • 4 large free range eggs
  • 2 tsp vanilla essence
  • 330g self-raising flour
  • 270ml butter milk (or mix 1 tbsp lemon juice or white vinegar with 250ml regular milk)
  • Red, yellow, green and blue food colouring (I used the supermarket liquid variety)
  1. Preheat your oven to 350F/180C bake. Grease and line 4 (if you have 4, I am unlucky enough to only have 2) 20cm/8inch cake tins.
  2. In a large bowl, cream together the butter and sugar until pale and fluffy. Add the eggs one at a time, beating thoroughly after each addition, along with the essence when beating in the last.
  3. Alternate between adding small divisions of the dry flour mixture and the butter milk until fully combined.
  4. Divide the cake batter into four bowls, dye each according to the intensity of colour you’re after.
  5. Pour into cake tins and spread out evenly using an offset spatula. Bake for 25-30 minutes until a skewer comes out clean. Cool in the tins for half an hour before removing to cool further to room temperature.
  6. Wrap in cling film and freeze until the day of serving (up to a month!).

And the Swiss meringue buttercream (via Sweetapolita):

  • 10 large, fresh egg whites (300 g)
  • 2 1/2 cups (500 g) sugar
  • 680g unsalted butter – left to reach room temperature from the fridge for ~1 hour, cut into cubes
  • 20ml pure vanilla extract
  • pinch of salt
  1. Wipe the bowl of an electric mixer with paper towel and lemon juice, to remove any trace of grease. Add egg whites and sugar, and simmer over a pot of water that just touches the bottom of the bowl, whisking constantly but gently, until temperature reaches 160°F, or if you don’t have a candy thermometer, until the sugar has completely dissolved and the egg whites are hot.
  2. With whisk attachment of mixer – or a hand beater, whip until the meringue is thick, glossy, and the bottom of the bowl feels neutral to the touch (this can take up to 10 minutes or so). The key here is patience: make sure the egg whites are not warm at all!
  3. Switch over to paddle attachment (or continue to use your hand beater, as I did) and lower the speed. Add the butter cubes, one at a time, beating well so they are smoothly incorporated. Mix until it has reached a silky smooth texture (if curdles, keep mixing and it will come back to smooth). Add vanilla and salt, continuing to beat on low speed until well combined.
  4. I found storing this in the refrigerator to change the texture of the buttercream despite attempting to whip it back to life – I would make it prior to decorating.

And finally, the candy melt cake drips:

  • 150g blue Wilton candy melts
  • 50g white chocolate in pieces
  • 60ml cream
  • 1 tbsp corn syrup
  1. In a small saucepan, heat the cream gently until simmering (this takes less than a minute, so keep your eye on it!). Stir in the candy melts, chocolate and corn syrup immediately, mixing constantly until combined and smooth.
  2. Set aside to cool slightly before pouring onto the frosted cake.


  1. Remove the frozen cakes from the freezer, and unwrap the blue base layer. Use a small dab of SMB to secure it to your cake stand. Spread enough of the buttercream evenly across the top of the blue cake, right out to the edges. Place the green layer on top and repeat the buttercream spreading. Repeat again with the yellow, then place the pink on top.
  2. Make a quick crumb coat by spreading a thin layer of the buttercream over the entirety of the cake – this can be as messy as you like, it just makes for a better base with which to decorate the cake smoothly. The frozen cake will “chill” and set the icing of its own accord in about 10-15 minutes.
  3. Finally, frost the entire cake evenly with the Swiss meringue buttercream using a metal spatula. Achieve perfect smoothness once it’s covered by using the spatula, heated with some hot water then dried each time, to even out any imperfections.
  4. Refrigerate the cake for half an hour to ensure the Swiss meringue is cool enough for the candy melt drips to set on top of. When set, pour the cooled ganache on top of the cake, using the spatula to push the drips out to the edges where they will fall as they may.
  5. Decorate the top of the cake with a crescent of crushed meringue, whole meringues, blue sugar pearls and M&M’s.



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