Making a Geode Cake – at home!

photo-08-09-2016-19-19-09On a daily basis (and mostly around a time that I should be sleeping) I drool over pretty pictures on Instagram, mostly coming from Tortik Annushka, Whipped Cake Co or Coco Cakeland. And who can blame me, I mean these cakes are so, so beautiful! Now to make something in that category is off course a complete different ballgame in terms of added life quality.

The good news is that I think this Geode Cake came together relatively easy, especially if you have baked standard layered cakes before (if not, this guide and these tips might come in handy). I would lie if I tell you that it is quick, because it is not, but if you are looking for a fun project, then I would say, roll up your sleeves and get going. And to add an argument in the mix: mono-tasking and relearning the art of patience are totally cool these days.
Rather than giving you a recipe, I am giving you a list of tips and required ingredients / tools below. It took me quite some time to figure out what would be the best / easiest way to do this and am happy to share my experience so that you can save yourself some doubts and time.
Have fun (and please don’t hesitate to comment in case you have questions)!

A short summary of my main tips & tricks:

  1. Make sure that you hand-color your sugar crystals, it will make your cake 1000 times more elegant.
  2. Be careful with cutting out too much cake for your geode, less is more – plus the cake made into ‘geode’ is inedible due to the rock-hard sugar, you will have to slice around it.
  3. Try to avoid heavily colored cake-filling and rather opt for something that is a little more sturdy, non-drippy, like white-chocolate ganache or fudge. (I used strawberry marmelade and really had to work around the red bleeding into the geode).
  4. Try to work as precise as you can, and whenever you seem to get frustrated, place the cake in the fridge and make yourself a nice cup of tea – it will get easier.
Making a Geode Cake – at home!


  • 1 finished (white) smooth-frosted (layer-)cake (I made this Italian Buttercream layer cake)
  • 1 cup of extra frosting
  • 1 sharp knife and a spoon
  • Rock Sugar - uncolored (I bought something called 'Kandis' in German or 'kandijsuiker' in Dutch - which is way cheaper than buying rock-sugar sticks)
  • Food coloring - I used Wilton's gel colors (from the basic collection 'Violet' and 'Black')
  • A small brush
  • 1 tablespoon of clear alcohol, such as vodka
  • Pestle and Mortar (to smash the rock sugar in to smaller pieces)
  • 1 tweezer (either brand new and super-clean or one bought from a pastry shop)
  • Gold Leave, around 8-10 leaves
  • A larger brush (wider) to apply to gold leaves
  • (If you want to transport the cake: a sturdy cakeboard that is larger than the diameter of your cake)


  1. To start off: my main aim was to make a cake that is elegant. When I was looking around online, it seemed like a lot of home-made geode cakes on Pinterest lacked a certain finesse, due to the fact that the rock sugar was monotone in color and left in too big pieces. Another mistake is - from my point of view - is to cover too much of the cake in 'geode' construction.
  2. And by all means - I tried to avoid the lady-parts look at this geode (and I don't even know how to say this differently but once you start to look at the Pinterest pictures from that perspective it is hard not to laugh out loud).
  3. So, to achieve all of this: start with coloring your rock sugar. You might want to get a head-start on this and do this the day before you build up your cake to make sure the pieces are dried (and thus easier to handle).
  4. Use three small bowls (I used egg cups for this), and place vodka in one, and the purple and black food coloring gel each in one as well.
  5. Get a piece of baking paper and place the rock sugar on it.
  6. The amount pictured was (to my surprise) way too much for one cake, I would estimate I used 20% of that.
  7. Take the small brush and dip this in the vodka and then in the foodcoloring. I added more vodka to the coloring between coloring some crystals to create different shades of black and purple.
  8. In any case, be sure to not color around 30% of your crystals, to keep the appearance of your geode natural.
  9. After the sugar crystals are dried (for me it took around 24 hours), place them in a pestle and smash carefully with a mortar. I can imagine that this would also work between two wooden boards or with a dough roller. Be careful to leave enough bigger pieces to work with.
  10. Now get a cold, frosted cake (I made a layer cake with italian buttercream and carefully mark the surroundings of your geode.
  11. I marked the outer linings with a little wooden pick, to make sure I would make too big of a hole in the nice cake.
  12. Then, carefully cut into the cake where you drew the line and use a spoon to deepen the space. Be careful as you don't want the pieces of cake to drop against the rest of the smooth outside of your cake.
  13. Also keep in the back of your mind: all the cake you are making into a geode, is cake lost, as nobody wants to chew on rock-hard pieces of sugar.
  14. Then, use the extra frosting that you have on hand to line the inside of the gap you made in the cake. You will need this to stick the pieces of sugar in.
  15. After you have carefully covered the inside of the cavity with buttercream, you can shortly place the cake in the fridge (for about 15 minutes). This will make everything more firm and easier to work with. Having said that, it might also make it more difficult to get the sugar crystals to stick.
  16. Try to find out what works for you.
  17. Now place yourself on a chair in front of the cake (to avoid your hand from shaking - unless you are wayyyy cooler than I am that is;)) and start placing the pieces of sugar in the cavity, placing the darker ones on the inside, brighter ones to the outside.
  18. This is all a matter of taste and you can spend as much (or as little) time as you like.
  19. Then, when you have applied sugar crystals in all of the cavity and can't fit in anymore, have a look at the color. Do you like it? If not, you can still amend it a little by using the same paint as you used to color the rock sugar and carefully put it in there. I thought this was really scary, but this way I was able to fine-tune the looks of the geode.
  20. Let your cake firm up in the fridge before you continue with the last step, applying the gold leave. Then, when the cake has sat in the fridge for around 2 hours, take out a larger brush and the gold leave. With help of the brush, carefully place the gold leave around the geode. This is a messy process and the leaves will often tear up - I'm afraid there is not much to do about that and my advice is to let it go and roll with it. It seems like it always ends up being truly beautiful.
  21. After you have added gold leave to your liking - your geode cake is ready!

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    • Eline October 31, 2016 / 12:45 pm

      Thanks! Looking forward to your results 🙂 x

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