Earth Structural Layer Cake

A little while ago, my sister approached me with an idea. She’s doing an education degree, and her and her friends had to give a series of lessons on the geological sciences to a class of primary school kids. One of their lessons involved teaching the kids about the structure of the Earth. One of her friends came up with the idea of presenting a model of the Earth made out of cake. So my sister asked me if I could make a spherical cake with all the layers of the Earth inside it.

I told her I couldn’t do it. “How do you get a sphere inside a sphere inside a sphere?” I recall saying. “Oh yeah,” she replied, realising what it would involve.

I spent the rest of the afternoon thinking about it. I don’t admit defeat. Ever. But especially not with cake. Nothing is impossible is pretty much my baking motto, so to say this cake was impossible left me feeling weird. There had to be a way. A way that didn’t involve carving or crumbing the cake. I kept mulling it over until I had a breakthrough.

There was a better way of doing this that I came up with, but I needed a set of hemisphere tins to pull it off. I didn’t have the equipment, nor the funds to purchase it, so I had to come up with a plan B. Somehow I went from “it’s impossible” to having multiple ideas. Go figure.

Plan B involved baking a cake inside a cake inside a cake. And crossing all fingers and toes and hoping it worked.

Looking pretty promising so far.

There weren’t enough people to warrant a complete sphere, so we went with a hemisphere globe instead. With the inner core, outer core and mantle all cake-d up, it was time for the crust. Chocolate buttercream filled that role.

The rest was left up to marshmallow fondant.

Depictions of the globe, satellite pictures of the Earth, movies… they almost always seem to show the globe featuring America smack bang in the middle. I’m always surprised and excited to see it any other way. So this time I let my home country by the focal point of the cake, and based everything else around it. America still got a little peep around the side.

I added a little white and marbled it into the fondant to make some clouds. I hand cut all the continents from fondant, then painted them with a gel paste mixture using a dry brush technique. This process all up took me about 6 hours and was the most arduous process. Coupled by the fact I was using the world’s tiniest brush. But I think the different colours makes it look much better than if I’d have used plain green fondant.

When I started this cake I was determined for pin-point accuracy. I was going to make every country and every island so damn accurate a pilot could use it as their navigation system. But by the time I got to Europe, it was more like, “Yeah, that’s the general shape.”  By the time I got to the Americas I was wondering if that continent was even necessary. I missed a whole heap of islands above Australia and settled instead for the main ones. Cutting out the countries wasn’t that cake walk I’d imagined it to be.

I finally got to a finished look for the cake and let my sister take it off my hands. She brought me back a slice so I could share a picture of the inside with you all. The red layer is orange Madeira sponge, the yellow is lemon Madeira sponge and the white cake was a vanilla buttercake.

And one of her friends sent me some pictures of their cutting out the cake.

It wasn’t an image of perfection, but I was just relieved that the layers were there. I ran into a lot of trouble with the yellow layer simply through this being one large experiment, so I was expecting it to be a mish mash of terrible proportions.

I’d definitely change a few things next time I tried it. I’d especially love to try the Plan A version of it one day, for that would allow toe possibility of using more moist cake recipes.

I’m told the cake was a massive hit with all the staff and students, so that was definitely a relief!

ETA: Tutorial for making a concentrically layered cake is now here.


170 thoughts on “Earth Structural Layer Cake

  1. What is marshmallow fondant and can it be vegetarian? Marshmallow sweets usually contain gelatine and vegetarian marshmallows are not available in Poland. 😦

    • Marshmallow fondant can only be vegetarian if the marshmallows are, given that it is made from melting marshmallows. As an alternative you might want to look at regular fondant. Some of it is not vegan as it contains egg white, but it is vegetarian. Alternatively you can make marshmallows from scratch using plant-based gelatin, but that’s quite some effort.

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