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Coolest Rainbow Fish Birthday Cake

My 6 year-old son was having his first ever birthday party at a local aquarium, so a homemade rainbow fish birthday cake was a logical choice. Naturally I came to ‘Coolest Birthday Cakes’ for inspiration !

I made two 8″ round butter cakes from a generic butter cake mix and let them cool, then wrapped them in aluminum foil and froze them. Freezing cakes prior to icing has a twofold advantage:

1) It breaks the project down into two steps – baking and decorating (very important for time-poor mums as the cakes can be baked weeks ahead);

2)Icing a frozen cake is much easier as it helps with the perennial ‘crumbs in the icing’ problem.

I left one cake whole to form the body. The second cake was cut up to make the tail and fins. The cake was iced with blue butter cream. This is where I ran into some problems! Despite having frozen the cakes, I still found problems with crumbs in the icing and the icing not sticking to the cake properly and peeling off along with the top layer of the cake exposing even more crumbs !!

Then I remembered a little trick I use when preparing meatballs… after I have made my meatball mix, I wash my hands thoroughly, then wet them under cold running water – shaking off the excess. This seems to stop the mince mixture sticking to my fingers as I roll the meatballs. So… I abandoned my spatula and knife, washed my hands and then ran them under cold water and shook them dry. I then added more icing and spread it over the cake using MY FINGERS. It was SO EASY to smooth out the ‘mistakes’ and correct the finicky areas around the fins and tail.

NOTE: don’t over-wet your fingertips as the icing will turn into a runny mess. Having gotten over my ‘icing stress’, I used a fork to emphasize the face, fins and tail of my fish, then proceeded to decorate the body using smarties.

I bought a 1kg bulk pack of Smarties from a confectionery warehouse which seemed to provide a much nicer range of colours than the standard supermarket packs (there were three other colours that I didn’t even use on my cake). I presorted the smarties by colour so that I could easily see how many of each colour I had so that I could complete my desired design.

After forming the coloured stripes on the body of my fish, I saw that I had plenty of blue smarties left so I used these to outline the rest of my fish. I made lips out of two pink Jelly Beans and the eye was formed from a flattened marshmallow with a blue Smartie attached to the centre using icing.

My kids loved this homemade rainbow fish birthday cake and it was quite easy to put together.

2 thoughts on “Coolest Rainbow Fish Birthday Cake”

  1. Thank you. I made the cake for my son’s second birthday on the weekend. It was a huge success and so easy! Your instructions were great.


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