A Rubik’s Cube Cake

My little one turned 6 and I baked him a Rubik’s cube cake.

So he was the boy who brings the Rubik’s cube to school every day. He would fiddle with his cube while waiting for me to fetch him after school and was quite sure he wanted a Rubik’s cube cake for his birthday. I tried convincing him into bringing a Minecraft cake instead, since the last one I baked turned out to be quite a hit with the kids. He was agreeable for a while but changed his mind the next day. I went ahead to have something Minecraft prepared, just in case he changed his mind or my Rubik’s cube cake failed!

A week prior to his birthday I started looking for alternatives to baking a full size Minecraft grass block. I found a clever idea to turn rice crispies into blocks without having to bake up a storm. It was as simple as mixing rice crispies with some sticky chocolate and have them chilled in the fridge.

The recipe uses melted marshmallow and chocolate candy melts to coat the rice crispies and then have them pressed in a baking dish before popping the dish into the fridge. Once chilled, cut up the hardened rice crispies into square pieces and have 2 squares stacked on top of each other to create a grass block. Use green buttercream frosting to pipe on the ‘grass’ and there you have it, a delectable grass block. I was quite sure the kids would love it as it’s hard to go wrong with Chocolate coated rice crispies!

Because I wasn’t comfortable feeding his friends sugary marshmallows that come in big 2 dollar packs, I substituted the marshmallows and chocolate candy melts with chocolate Ganache made from Chocolate couverture and cream. Lined these blocks together to form a bigger grass block and it looks almost as good as a cake at half the effort.

After setting in place a back up plan, I went on to work on the Rubik’s cube cake, I did a trial bake the week before and I was glad I did. It took me 3 days of baking, frosting and decorating it with fondant and I secretly wished that the birthday boy would change his mind and opt for the rice crispies grass blocks instead.

First look at a Rubik’s cube cake; a cake that is made from multiple square cakes, stacked together to form a cube. There are 5 faces (minus the face that will be sitting on the cake stand) that need to be decorated, each face with 9 squares. It looks pretty straightforward with little imagination required. No fancy idea required to crush cookies to create ‘dirt’ or cover up flaws (unlike the Minecraft birthday cake).

I soon learned that making a Rubik’s cube cake wasn’t about creativity. It was about precision. From choosing the size of the baking tin to deciding on the number of layers required and cutting each squares to fit onto the blocks, everything needs to be precise and it got quite mathematical along the way.

Here are some of the mistakes I made while making the cake and I thought it would be great to compile these lessons learned.

Mistake #1 Do not take short cuts unless you are very sure it leads you to the same result

Instead of getting 3 cake tins of the same size and baking in 3 separate batches, I did everything in 1 batch with whatever size cake tins I had.

I used a 7 by 7 inch baking pan and a 13 by 9 inch baking pan thinking I could trim the 7 inch cake and patch up a 6.5 by 4.5 inch one (by diving 13 by 9 inch into 2) to get a 6 inch cube. I ended up spending a long time trying to ‘perfect’ the cube coating it with crumb coat.

Tip : Use baking pan of the same size for all the layers. It’s more worth it spending the time baking proper size cake than to spend the time patching an odd size one. The result of the latter isn’t guaranteed.

Mistake #2 Don’t be obsessed with fluffiness

I needed a cake recipe that was dense enough as I had read how the weight of fondant might crush the cake. I decided to go with a butter cake recipe from here with raving reviews.

I also read how cake flour could make a cake fluffier. I decided to replace self raising flour with cake flour I had and adding a tablespoon of baking powder to it. Bad idea!

My cake turned out soft and fluffy and it was so difficult to handle. The cake broke into half and crumpled into pieces even before I could stack them up!

Tip : A butter cake is a great base cake for a fondant cake because it is dense and could hold the weight of the fondant. So save your soft and fluffy cakes for other occasions.

Mistake #3 Hand painted fondant doesn’t give you even colour

I thought I could hand paint the fondant like what I did for my Minecraft cake but the end result was patchy colours. A Rubik’s Cube is much less forgiving when it comes to colours. You can colour a Minecraft grass block cake with different shades of green and it will look natural but for a Rubik’s Cube cake, it has to be solid even colours.

I sticked to the conventional way of colouring fondant during the actual bake, ie. by mixing colour gel to white fondant. The colours did turn out smooth and even but in a lighter shade. I thought I could live with that little imperfection so long as I didn’t have to add copious amount of food colouring to the cake.

Tip : Buy ready coloured fondant if you need vibrant colours. You’ll save a lot time trying to get the colour right colouring white fondant. However if you are ok with pastel colours, white fondant is great. There’ll be less wastage, more flexibility and it is cheaper.

Mistake #4 Whipping thickened cream is different from heavy cream

I used chocolate ganache for the icing and the recipe called for heavy cream which I substituted with Whipping Thickened Cream as I can’t find the former in our local supermarket. The chocolate ganache turned out runny. I did manage to frost the cake but I had to leave it in the fridge for the ganache to harden before decorating it with fondant.

Tip : Use Thickened Cream in replacement of Heavy Cream. Whipping cream is different even if it’s the thickened kind

Mistake #5 Fondant ‘sweats’ in humid Singapore weather

I couldn’t decorate the cake with fondant in a go and had to store it in the fridge till I had time to continue. Because of the change in temperature and humidity, water started to condense on the surface of the chocolate ganache when the cake was brought out the fridge. This caused the fondant to ‘weep’ and ‘sweat’.

Tip : Store your finished fondant cake in a cool room, preferably an air conditioned room. Avoid drastic change in temperature as it will lead to condensation and thus cause the fondant to melt.

Thankfully most of these mistakes were made during the trial bake and I could prevent making the same mistakes on the actual bake. My boys loved the cake and the children in school wiped out every single bit of it.

Will I bake this again?

Probably not.

But knowing how forgetful I am when it comes to painful bakes, it shouldn’t be long before I dive into another arduous bake.

Here’s another post I wrote on Tips for making cake pops



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