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Sprinkle Geode Cake Tutorial

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Now, don’t get intimidated by making this cake. That is the best advice I can give you when it comes to trying out something new. Intimidation is what stops me, it’s what’s stopped me from making macarons and cheesecake! Two things I still have to make this year because I’m not going to give in.

However, when it comes to decorating this cake, I promise you, it’s little steps at a time, and to be honest, you don’t even have to do them all! You get to pick which ones you do from this cake. In this tutorial, I’m going to show you how to do a Sprinkle Geode, but I’m also going to give you the recipe I used for making a box cake mix taste homemade, and tell you the tricks to getting the painted look on my cake. Lastly, I’ll tell you my secret for that rock candy sticking out of the top!



Box Cake to Bakery

Here’s the trick! You’re going to add to the ingredients on the box cake mix instructions. As easy as that. 

  • 1 box Cake Mix
  • 1 extra Egg from what the box says
  • Unsalted butter Replace oil with melted butter
  • 1 Tbsp Vanilla
  • Milk Replace water with milk
  1. Follow the same instructions that are on the cake mix, with these alterations

  2. Add 1 extra egg from what the box says 

  3. Don’t use the oil, you want to use melted butter in its place (unsalted) 

  4. Add 1 Tablespoon of Vanilla

  5. Replace the water, it calls for, for milk

  6. Bake according to directions on the box

For this cake, I baked a strawberry cake! I also used fresh strawberries in between the layers, and my American Buttercream recipe which you can find HERE in my Pinata Cupcake post. I used one box cake with the modifications above and cooked it in 3 6″ rounds. Be sure to coat all sides (and bottom) of your cake pans with butter, pam is fine. I always place parchment paper at the bottom of my pans as well.



Now that you’ve got your cake and icing, here’s a few things you need to know before we start:

  • You want your cake to be room temperature, if not cold. A warm cake will make your icing melt and that will be a disaster.
  • The fridge is going to be your friend. You’re going to place the cake in there several times during this process so clear out space for a tall cake.



Here is a list of the supplies I used for decorating, modify as you’d like!

Again, you don’t have to do every technique I do on this cake! Just pick the ones you want.



Now, you’re ready, let’s decorate this cake!

Step 1: Stack and Crumb Coat

  • Place a layer of your cake down, and then, if you’re going to add strawberries you want to do a thin layer of icing on the top of that layer, then a thicker border all the way around. Place the strawberries in the center, then add your next layer. Continue until you reach the top.
  • Add a thin layer of icing all over the cake. This is the crumb coat. You will still be able to see the cake, but the idea here is to catch all the crumbs so that way the crumbs don’t show up in your final decorated cake.
  • I then reinforced mine because I didn’t listen to the first set of instructions when placing the strawberries and my cake layers were sliding. If you want to reinforce just grab some extra straws you have, place them in a triangle in the center of the cake and then cut the tops off with scissors.
  • Put your cake in the fridge for 30min-1hr, you want the icing to get hard and no longer be sticky to touch.



Step 2: (not pictured) Add your second layer of icing

  • For this layer I used white, but whatever you want the main color of your cake to be, that’s what you want to use
  • Cover the entire cake, here are some tips:
    • Put a few big dollops on the top
    • Use a piping bag (you don’t need a tip for this, just cut a hole at the end) and pipe along the sides
    • A lot of icing is good! You’re going to smooth it with your scraper or spatula and some is going to come off. Have a bowl handy for you to scrape off excess icing
    • For this cake, you’re going to go over the top with your colors so you don’t have to have perfectly smooth icing (woohoo!), but if you’re going for that, keep smoothing it with your icing scraper, and heat it up with warm water if you need to.
    • Put your cake in the fridge for 30min-1hr, you want the icing to get hard and no longer be sticky to touch.



Step 3: Add your colors

  • Take your piping bags full of the colors you want (I used red and blue) and randomly place some dollops on the sides of the cake. Not too many!
  • Then, take your spatula or scraper and smooth it out again. You’ll get this painted look! You can always add more color so don’t do too much at the start, add as you need, and remember that layers are good.
  • Put your cake in the fridge for 30min-1hr, you want the icing to get hard and no longer be sticky to touch.



Step 4: The Sprinkle Geode

  • It’s time to cut a hole in your cake! This can look however you want. Decorators choice.
  • After this, you’re going to use your spatula to cover the sides of the hole with icing.
  • The reason you want to have refrigerated before is that the only icing you want to be sticky is what you just put on the hole you made. You want the sprinkles to stick to that and nowhere else.
  • Now, grab a small spoon and slowly cover all that icing with sprinkles. I used my hand as well, and yes, sprinkles are going to get everywhere! To save myself from cleaning sprinkles for years I placed a large cookie sheet under the cake to catch the sprinkles. It didn’t catch all of them, but it helped.
  • Some of my sprinkles did fall down on the cake where I didn’t want them, but I just carefully removed them, then smoothed that area with my spatula. That’s the beauty of this cake, you can’t really tell where the “mistakes” are!

Step 5: Gold

  • Cover the edges of your sprinkle geode with luster dust. I just slowly used my brush and went along the edges. I’ve also heard you can create more of a paint with your luster dust combining some of it with a little bit of vodka or lemon juice. I’ll try that next time!

Now, you could totally stop here! I think it looks amazing just like this and I almost stop… but then I didn’t, and went over the top.



Step 6: Add the rest of your decor

  • Carefully place your stars all over the cake, and use some luster dust to give them a “shooting star” effect.
  • Use a piping bag and your favorite tip to pipe swirls along the top in a circle, and then add sprinkles there and a few in the middle if you’d like!
  • Finally, add your painted rock candy.
    • Use luster dust to paint one gold
    • Add water or vodka in a small bowl with a tiny drop of your color to be able to paint the red and blue candy

Refrigerate when done!




Will you be using any of these tips for your next party? What do you want a tutorial or recipe for? If you loved this post, I would love it if you shared it on Pinterest using the image below!


Have you seen the amazing cakes floating around on Instagram lately? Well I promise you they're not as difficult as they look! You can easily create this sprinkle cake geode for your next event. I'm not a professional baker and I did it! Check out this post for step-by-step instructions plus a recipe for making a box cake taste homemade.

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Hi! I'm Bree

In my day-job, I teach amazing individuals how to make money with their blog and social media! I started blogging back in 2010 as a hobby, and it turned into my dream job—helping women make their own money on their own terms. Blogging became a job that I love—now, I’m back to use this online journal as a fun place to document my life so I can look back 20 years from now and remember all the magical things. 

I use baking as a way
to de-stress...

And I love to play hostess and make my guests fabulous cocktails...