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Buttercream Galaxy Cake Decorating Tutorial

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Decorate your own out of this world cake with this easy to follow buttercream galaxy cake decorating tutorial!

Decorate your own out of this world cake with this easy to follow buttercream galaxy cake decorating tutorial! Video and all the details on

It’s about time we had another decorating tutorial, isn’t it, darlings? This one is super cool because not only will I show you how to decorate a galaxy cake with buttercream frosting, I’ll also give you the tips you need for making a black buttercream without using a ton of gel food coloring. Shall we get started?

Don’t I need to make a mirror glaze for a galaxy cake?

No. If you want the super shiny mirror glaze look, then yes. But if you’re just looking for a space-tastic cake with trusty buttercream frosting, here’s your guide. You can use a surprisingly easy technique I demonstrate in the video to create a lovely color swirl that gives that great space look with minimal fuss. And since most people love the flavor of buttercream, it’s a win-win.

diy smash cake tutorial

What supplies will I need?

To make this cake, you’ll need a turntable. An inexpensive one from the craft store will do just fine. You just need to be able to rotate your cake smoothly. And a bench scraper or large straight edged spatula. This is to smooth your sides and help spread and “swirl” the frosting. Beyond that, you shouldn’t need to purchase anything special. I have included a full list of materials used both in the video and in the “how to” at the bottom of the post.

Is there a special kind of cake or frosting I need to make?

Make whatever kind of cake makes you happy that layers well. Even a box mix will work! I do recommend using a homemade frosting to decorate though. Store bought/prepared frostings from the grocery store won’t have the right consistency. Maybe the “decorator’s frosting” from the craft store would work, but I haven’t worked with it, so I can’t vouch for the results.

easy outer space cake tutorial

I used a batch and a half of my Swiss meringue buttercream frosting recipe for this cake, with a little added chocolate melted in to help create the true black color. But a classic American buttercream will definitely work too. Make some just regular vanilla for your lighter colors, and then mix up a batch of my chocolate buttercream using the black cocoa powder instead of regular and maybe a few dots of black gel coloring to get the black color.

What about the finishing touches?

I add the finishing touches to this cake using a splatter paint, a little dry dusted edible shimmer dust, and sugar stars. Other fun options might be fondant planets or rocket ships if you want to add something cute.

Really, whatever you choose to add is up to you. This cake is very open to creative freedom. Just make sure you step back every once in a while to make sure you aren’t leaving any empty space where you don’t want it, or aren’t going too overboard. As you can see in the photos and video, I started with a simpler cake, and then decided to add more embellishment. Both are beautiful, but different.

space themed party cake tutorial

I’d definitely recommend grabbing a cup of water/coffee/tea/lemonade and watching the video. Not only will you get great tips – like how to get that rich black frosting without using a TON of gel coloring – but I think some of the text instructions will make more sense. This is especially true if you are new-ish to cake decorating. I can’t tell you how many times I read instructions and didn’t “get it” until I watched a video.

I really hope you enjoy this tutorial! If you follow it to make a cake, tag me please. I love to see everyone’s creations!

p.s. – If you want to know the story behind how this cake happened… an old wedding client of mine and I happened to be stationed at the same place some 5+ odd years later. She was looking for a smash cake, and while I’ve not made bespoke cakes in some time, couldn’t turn down this one. Celebrate life’s beautiful moments darlings, because they are truly a blessing.

Decorate your own out of this world cake with this easy to follow buttercream galaxy cake decorating tutorial! Video and all the details on

Buttercream Galaxy Cake Decorating Tutorial


Prepared Ingredients Needed



  1. Start with a chilled crumb coated cake. The cake can be whatever size you'd like, just make sure that you have enough extra frosting for your coating. I used about 4 extra cups of frosting to cover a 6 inch cake. For an 8 inch cake I'd have an extra 6-8 on hand.
  2. Color your frosting in your choice of galaxy inspired colors. Spread on the cold cake in patches. Be liberal! You may use a bench scraper or offset spatula for this.
  3. Use your bench scraper to even out the sides of the cake, working in sections and scraping off the extra frosting on the scraper as you go. Chill the cake 15-20 minutes.
  4. Fill in any gaps in the frosting as needed, making sure not to over-scrape the frosting to avoid mixing all the colors into one.
  5. Chill the cake another 15-20 minutes.
  6. Add frosting to the top of the cake, scrape across once in one direction, turn the cake 90 degrees and scrape in the other direction as shown in the video. Chill the cake again. Trim the edges.
  7. Mix a bit of your luster dust with a few drops of extract or alcohol to create a paste. Use your thumb to "splatter spray" galaxy droplets on a few spots of your cake. Add star sprinkles and additional luster dust as desired.
  8. Enjoy your creation!

Did you make this project?

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Friday 11th of December 2020

I'm in the middle of making this cake for the first time for my daughter's 13th birthday. 😁 I'm NOT experienced in any of this! But I followed your chocolate buttercream recipe to a T including black cocoa powder and the frosting is gray at best after emptying a full .7 oz thing of gel food coloring. Yikes. Any advice?

Mary (The Goodie Godmother)

Saturday 12th of December 2020

AHHH! I'm answering a bit late, but I hope the cake turned out beautifully! Black icing takes time to develop, so it's really hard to see the final color when you first mix it. So in the future, it's usually good to make the frosting and let it sit a few hours to see how to color develops. Given what you said you added to it, it should have deepened into a rich black for you.

I hope your daughter had a beautiful birthday!

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