Lego Cake

Lego cakeA few weeks ago I was asked to make a cake to be auctioned off with the proceeds going to the local Children’s Hospital as part of Give Me 5 for Kids fundraising telethon. I agonised for ages over what cake to make – well, not what cake,  it was always going to be a chocolate cake – but what shape the cake was going to take.

Would it have a big Give Me 5 for Kids logo on it? Would simplicity be best – just a huge, round chocolate mud cake, garnished with even more chocolate? I didn’t know.

But the more I thought about it, the more  I realised that the cake had to cater for the kid inside all of us. The one that ate Milo right from the tin and licked caramel off grubby fingers.  Most of all, it had to look the goods – it had to evoke that ‘take me back to my childhood’ feel. And so, I settled on Lego.

There are so many ways to make Lego cakes, and I considered (as well as actually tried) a few of them. For a start, I considered moulding Lego bricks using a silicon mould and coloured chocolate melts or gumpaste. Great idea – they’re easy enough to mould, and I would get perfectly uniform bricks that I could just stack on top of the cake – But with the thickness of the bricks, I realised that the cake would be almost impossible, or at the very least, very difficult to cut. (I ended up using them at cake toppers instead). What if I made thinner bricks then, and stacked those on top of the cake – well I tried that, and it was stupendously difficult to get an even thinness of bricks. And so I turned to never-fail fondant.

It’s a fairly mathematical process, and really isn’t too difficult at all. I’ve assumed a basic level of knowledge of baking, torting and ganaching cakes. If you don’t already know how to do those things, a lot of this information can be found online. Apologies for not including any photos of the process, the cake was a fundraising project and I didn’t actually think that this post would make it to the blog.

This should be an easy enough project if you set aside enough time. And buy pre-coloured fondant. Because buying white fondant and colouring it yourself is just fraught with danger because it can leave you with colouring absolutely everywhere

You’ll need:

  • 1 x 8″ square cake tin
  • 2 x 8″ square cake boards
  • palette knife
  • metal pastry scraper
  • 4-5 colours of fondant (yellow, red, blue, green and black)
  • rolling pin (bonus if you have a pasta maker)
  • ruler
  • utility knife/stanley knife
  • a plastic drinking straw (for cutting circles)
  • small paintbrush

Start with making the chocolate mud cake – you’ll find all the instructions here. Make sure to use an 8″ square pan – because there isn’t such a thing as rounded Lego. And most importantly, bake a in a conventional, not fan-forced oven.

Tort/cut and fill the middle layer of your cake with ganache. Using a palette knife, smudge a bit of ganache on an 8″ cake board (to hold the cake in place), then put the cake on the board making sure to check it is centered. Ganache the cake – this should take about 1-2 hours, and if you need instructions, you’ll find them here.

Once you have a fully ganached cake, we’re going to go to the tricky part – covering the cake in fondant and getting the Lego bricks on. Brush the cake with a thin layer of syrup and cover the cake in a base layer of fondant – it doesn’t have to be perfect as we’ll be tiling the ‘bricks’ on after, so just make sure you get a nice even layer of fondant.

The fully ganached cake, covered in fondant should be just under 80mm high.

We’re going to now work out the size of the bricks –

  • Measure the height exactly, then add 2mm to the measurements to adjust for the thickness of the fondant. For instance, my cake was 78mm high + 2mm = 80mm.
  • Divide 80mm by 5 = 26mm (the bricks will be 16mm high)
  • Measure the width of the cake exactly, then add 2mm to the measurements. Mine was 206mm +2mm = 208mm.
  • Divide this by 4 = 52mm (the bricks will be 52mm long)
  • Divide the length of the brick by 2 to get the width = 52mm/2 = 26mm.

Therefore, each side of cake will be made up of 20 rectangles (5 high and 4 wide) measuring 26mm (w) x 52mm (l) x 16mm (h).

  • There are 4 sides, so you’ll need 80 rectangular pieces for the sides, and 32 pieces for the top of the cake.
  • Roll out some extra fondant – you’ll need it to cut the little circles that make the cake look like Lego.

Now, start rolling and cutting the fondant to make these rectangular pieces. I used a pasta roller (just turn it backwards, past the widest setting) which was about 2mm thick.

  • Start with the lightest colour fondant – this is always good practice as some residual colour can stick to the rolling pin or pasta roller.
  • I recommend rolling the fondant, setting it aside to air dry and firm up a bit before cutting it into strips. Then cut across into rectangles. So, start with the yellow, leave it to firm up a bit on the bench and by the time you’ve rolled out the other colours the yellow fondant will be firm enough to cut.
  • For the sides of the cake, cut some of the rectangles in half widthways/crosswise so they look like you’ve stacked the bricks at 90 degree angles i.e. they should measure 16mm by 26mm.

Time to start assembling the Lego cake.

  • Brush one side of the cake with syrup to help the fondant stick.
  • Start at the bottom of one side and ‘stack’ five bricks on top of each other – you should just see an extra 2mm of fondant at the top of the cake. If this hasn’t happened – uhoh – the measurements are wrong – start again, from the top!
  • Starting at the bottom layer again, work your way across sticking on one brick at a time.
  • Keep stacking – make sure to mix in some of those half bricks to make it look more interesting!
  • Move on the next side of the cake, don’t forget to brush with syrup and remember to pay attention to the Lego colours – the colours need to cross around the corner to make it look like real bricks.
  • Work your way around the cake, paying attention to the corners, to make sure they match. When that’s all done, hurray – you’re most of the way there! It’s starting to really look like Lego now.
  • Time to start tiling on the top – brush the top with syrup, then start tiling at the outer perimeter of the cake, making sure to line up the bricks to match in colour. This is the fun part!
  • When that’s all done, start cutting out tiny circles using a straw. It’s a good idea to drop the straw in corn starch first. It’s going to take ages, so settle in. You’ll need 8 per brick for the top – that’s 256 circles of various colours.
  • Use a small paintbrush to dab on a tiny bit of water, then arrange the circles to look like Lego on top of the cake.
  • Once you’ve done that 256 times – you’ll have a perfect Lego cake. Take lots of picture and send it to your friends, you probably won’t be doing all that work again anytime soon!

If you liked this tutorial, please consider donating to your local children’s hospital, or to the Give Me 5 for Kids appeal.


  1. says

    Sounds amazing! I love working my way through recipes like this. I’m about to start a 12 week fitness challenge but will try this once I’m done! Quick question, does it have to be a conventional oven as I don’t think I can switch the fan off mine?



    • Tash says

      Hi Paul, I think making cake is a good way to not want to eat it (well it works for me). Baking this cake in a fan forced oven causes it to sink in the middle because in most fan-forced ovens the heating element is at the back of the oven. This causes an uneven rise, and every time I’ve tried it, it does leave a crater in the middle of the cake.

      • says

        Thanks, that makes sense as I had a similar issue when making macarons as the cases were quite flat. Think I may try and focus one of my impulsive purchases and buy a portable oven…$200 tops I imagine :)

        • Tash says

          I caved and bought an AEG off Gray’s Online at a really good price in Melbourne. Then my partner got a job in Canberra. It was so sad to leave my oven behind. I’ve never used a portable but that sounds like a good plan. Induction stovetops are also my new favourite thing.

    • Tash says

      Thanks Simon – was pretty fun to make, even if I did have to stay up til 2am because rolling and cutting out all the ‘bricks’ it took a lot longer than I anticipated. And then spent the next day cutting out circles with a straw…

  2. says

    I love it, but doesn’t anyone make fondant from scratch? (Noting the time I tried was a massive fail). And while I’m here, why are Thermomix used so little on Masterchef? I spend half the elimination tests yelling “use the Thermomix!!!” All that standing over the stove with thermometers when you are under time pressure…

    • Tash says

      I never did because in the Planet Cake book it said basically, don’t bother. Even they use bought fondant. Adding that much colouring to fondant is also a real pain.

      The Thermomixes have to be specially requested. Plus lots of people aren’t that comfortable using them, it seems.

  3. says

    That looks absolutely stunning Tash!! I wish I had those decorating skills :) I love to bake when when it comes to decorating I am way to messy.
    Now if my mum could just put that amount of effort in my birthday cakes that would be great…

    • Tash says

      Haha, if I was a kid I’d love that cake. Actually, even as an adult, I’d love that cake! Decorating is just good planning, a bit of practice and lots of attention to detail.

  4. says

    Wow – that is so awesome! At first, I thought you were having us on and simply made a toy cake out of lego pieces and then I realised that it really is an edible cake. It looks so real and amazing!! It’s a winner of a cake. :)

    • Tash says

      Thanks Padaek – was pretty fun to make too :) Even if it did show my slightly obsessive tendencies…

      • says

        I think it looks brilliant! Looking forward to following your blog and reading your other posts in detail. My partner and I really enjoyed watching you on Masterchef. We think you should have stayed a lot longer. Anyhow, always new things, right? Thanks and have a great week Tash! :)

  5. Erin says

    I searched for months for the perfect lego cake for my boys this year and gave up. But this I love! It’s beautiful!

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