Lego Birthday Cake

We are big Lego fans in this house. Everyone got some sort of Lego for Christmas this year. Yes even me! Whether I’ll get enough time to sit down long enough to build it at some stage, who knows!? It’s no big surprise then that a Lego cake was requested for my 5 year old’s birthday a few months ago. 
The boys’ birthdays are within two weeks of each other and inevitably each year I blog one birthday cake and forget to blog the other. This one has been sitting in drafts for a good 4 months. I am going to make the same sponge recipe soon for a Christening, so it was time to blog the recipe if only so I can look it up myself! 

This is the third time a Lego cake has been requested for birthdays in this house. Both this time and last time I ended up with the same basic shape – the square Lego piece. I made a chocolate version last time and this time it was lemon. You can see my very first attempt here

This time it was for a 5 year old. It had to be orange. And it had to have mini-figs on it. And real bricks at the side. This worked out super easy to make and looked pretty well with a ton of mini figs placed strategically on it.

lego cake

Lego Cake


For Sponge:

450g self-raising flour

250g margarine

550g caster sugar

4 eggs

320ml water

For Lemon Buttercream:

140g margarine

280g icing sugar

1 tblsp lemon juice

1 tsp lemon zest

For Royal Icing:

500g White Ready to Roll icing

Gel food colouring

To Decorate:

Lego pieces and Mini-figs

4 Jacobs Kimberley biscuits or 4 Oreo Biscuits.*

*(ensure to check ingredients in case they change but currently they are milk free) 

To Make Sponge:

  1. Grease and line a deep square baking tin or two shallow ones.
  2. Preheat oven to 180C / 170C Fan / 350F / Gas 4
  3. Sieve flour into a bowl, add the rest of the ingredients and beat together in an electric mixer or hand mixer until smooth.
  4. Spread out in baking tin.
  5. Bake for 30-40 minutes until a skewer comes out clean.
  6. Stand for 5 minutes before turning onto a wire rack to cool.

To Make Buttercream:

  • Beat the margarine until soft. Add half of the icing sugar and beat until smooth.
  • Add the rest of the icing sugar and the lemon juice and zest and beat the mixture until creamy and smooth. Add a little more lemon juice if necessary. 

To Ice:

  1. If the cake has risen slightly in the middle, carefully slice off the top to make it flat.
  2. Place the cake on a plate and freeze for up to 30 minutes. This makes it easier to ice with the buttercream. 
  3. Remove from freezer and cover with the butter icing. Use a palette knife or spatula to smooth it out. There is no need for this to be perfect as you will cover with fondant icing anyway. 
  4. Place 4 Oreos or Kimberley biscuits to make the connector pieces (bumps) of the lego piece. 
  5. I used a pack of white ready to roll icing. (Alternatively, mix icing sugar and water to make up your own – follow instructions on pack for ratio of water to sugar).
  6. Dye the icing whichever colour you desire. Orange lego was demanded here!  Using a cocktail stick, put a small amount of gel colour onto the icing and knead until the colour is uniform throughout. Add more until you reach the shade you want.
  7. Roll out the icing. 
  8. Using the rolling pin to help you, drape it over the cake and trim away the edges. 
  9. Decorate with real minifigs and lego pieces. Or if you’re very skilled make your own. 

lego cake

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