I’ve called this a quick how to as it’s not a step by step guide- at the time I wasn’t sure how it would work so this is more how I did it and what I picked up along the way.
- The key thing is it needs two layers of icing, if you try and stick the lego pieces straight to buttercream it’ll just creep up between the pieces and generally get sticky and messy. So first do one really thin layer of white (or marzipan), it doesn’t need to be neat and can even crack a bit, no-one will see. Then add lego and the main white icing layer. Stick the blocks using a pastry brush and a watery glace icing (icing sugar mixed with water), but in very very small amounts as the colours will run and spread everywhere.
- It’s best to have a template (baking paper works fine) to mark out the area you want to be lego. Mark this gently into the base white layer, then add the lego blocks. Use the template to cut this area out of the main layer of white icing when you roll it out before it goes on the cake (but leave it attached in the centre so you can roll it up once it’s on the cake). If you try and cut this once it’s on the cake the edges get messy and it’ll stick to the lego blocks and probably get nice blue smudges.
- The blocks are most easily done by rolling a flat sheet then cutting rectangles out of it. It’s much quicker than molding each one individually and if the edges are a bit rough they get joined together anyway. Same with the dots on top of the lego, it’s easier to make a long sausage and cut pieces off. The blocks on top will need individual molding though.
- A note on icing: if you’re UK based Asda is best by far in terms of price and range. You can buy a small pack of a selection of coloured pieces (which will easily do this cake twice over) for just over £2, Tesco and Sainbury’s charge that for one block of one colour.
- A square cake would have been easier…
Ice and Icing 
