Buttercream Galaxy Cake with step-by-step tutorial

Galaxy cakes are so beautiful but who wants to spend time making that galaxy mirror glaze and have it not turn out!? No one so I made a buttercream galaxy cake using American buttercream!

galaxy cake

Most galaxy cakes are made with a mirror glaze. Galaxy mirror glazes are made from condensed milk, white chocolate, water and gelatin to produce a shiny liquid topping that you pour over the cake. The black, navy blue, pink, purple, etc. create a marbling over the cake resembling a galaxy.

What cake to use for galaxy cake?

Any cake, even cake mixes are fine. I used my favorite vanilla cake recipe and it’s the base for a lot of my other cakes but you can certainly use any other 8 or 9 inch vanilla cake recipe. My only suggestion would be to keep it a butter/oil cake and not a sponge cake.

How To Make American buttercream?

American buttercream is incredibly easy to make. Essentially, the butter gets beaten with powdered sugar for 5-10 minutes. This ensures that the sugar is fully dissolved and the texture becomes fluffy instead of gritty. Add in the vanilla and cream, beating for another couple minutes.

galaxy cake with american buttercream

How to Make Black Buttercream Frosting

Black icing can be tricky to make but with a few secret ingredients, it’s possible. Obviously we’ll need black food coloring, just make sure to use GEL food coloring, it’s much more potent and will prevent the frosting from splitting. 

To avoid using so much food coloring in the buttercream I also used black cocoa powder to make a chocolate buttercream. This will also work with regular cocoa powder but you may need to balance the reddish hue with a drop of dark blue food coloring.

How to make a galaxy cake with American buttercream?

Galaxy cakes are easier than they look. I say that often but whenever something intimidates me, it turns out to be much simpler than expected. I’ve been wanting to make a galaxy cake but I was intimidated by mirror glaze so I just tried this out and it totally works. You don’t even need a piping bag!

  • Butter:  using room temperature butter allows you to incorporate more air for a fluffy buttercream and it will give you the right consistency for spreading frosting. 
  • Powdered Sugar: I find that it’s not necessary to sift powdered sugar if you beat it for 5-10 minutes, scraping the edges every couple minutes.
  • Vanilla Extract: You can also use maple or almond extract if you prefer but I add vanilla to EVERYTHING. 
  • Cream: This makes the buttercream creamier and more spreadable.  
  • Black cocoa powder: You don’t NEED this but it’s easier to make black buttercream using both cocoa powder and food coloring. Regular dark cocoa powder will work as well but I got good results with this black cocoa powder from amazon.
  • Gel Food Coloring: THIS WON’T WORK WITH LIQUID FOOD COLORING! Gel food coloring is much more potent. With liquid food coloring, the amount you would need would probably split the frosting and the colors would be a little off. I have this Americolor Gel Food Coloring set, also from amazon.
  • Offset Spatula and/or multi-purpose scraper: You don’t need both but they are both useful. Any of these would be fine, I prefer metal over plastic though. PRO TIP: when you use a metal spatula or scraper, heat it up under hot water before using it and it will spread the frosting so much nicer. 
  • Small paint brush: to create the white ‘stars’ in the galaxy, use a short, wide brush, similar to these in size.
vanilla bean galaxy cake

If the directions aren’t clear, make sure to watch the video (I’ve updated the recipe since but the method is the same). Hope you guys enjoyed this post & if any of you make this I HAVE TO SEE IT! Tag me @baranbakery on instagram. Leave a comment if you have any questions or requests for future videos/recipes, etc. As always, have a blessed day and happy baking!

Love, B

Yield: 10 slices

Galaxy Cake Recipe

galaxy cake

The BEST vanilla cake frosted with vanilla American buttercream, made to look like a galaxy.

Prep Time 1 hour
Cook Time 35 minutes
Additional Time 30 minutes
Total Time 2 hours 5 minutes


White Cake

  • 2 1/4 cups (270g) all-purpose flour, spooned and leveled
  • 1 Tbsp (10g) baking powder
  • 1/2 tsp salt
  • 1/4 cup (56g) unsalted butter, room temperature
  • 1/2 cup (118mL) vegetable oil
  • 1 1/2 cup (300g) granulated sugar
  • 3 large eggs, room temperature
  • 3/4 cup (170g) sour cream
  • 1 Tbsp vanilla extract
  • 3/4 cup (177mL) whole milk

Vanilla Frosting

  • 1 cup (227g) unsalted butter, room temperature
  • 3 3/4 cup (450g) powdered sugar, spooned and leveled
  • 2 tsp vanilla extract
  • 2 Tbsp (30mL) heavy whipping cream

Galaxy Decoration

  • 1 cup (227g) unsalted butter, room temperature
  • 3 3/4 cup (450g) powdered sugar, spooned and leveled
  • 2 tsp vanilla extract
  • 3 Tbsp (45mL) heavy whipping cream
  • 2-3 Tbsp black cocoa powder
  • Pink, blue, black & white GEL food coloring
  • Small paint brush


Vanilla Cake

  1. Preheat the oven to 350F/177C convection (or 325F/162C conventional) and grease and line three 6 inch cake pans. 
  2. In a medium bowl, whisk together the flour, baking powder and salt until they're evenly distributed.
  3. Place the room temperature butter, the oil and the granulated sugar in a large bowl and use an electric mixer with the whisk attachment to beat them for 2 minutes. 
  4. Add the eggs, one at a time, beating on medium speed until each egg is fully incorporated. Add the sour cream and vanilla extract and beat just until combined.
  5. Add half of the dry ingredients to the wet ingredients, turn the mixer on low speed and then pour in the milk, followed by the rest of the dry ingredients. 
  6. Distribute the batter evenly among the three cake pans, about 14oz in each pan and bake for 30-35 minutes. When the cake is fully baked it will release itself from the edge of the pan and it will spring back if you press on the center of it. 
  7. Allow the cake to cool completely before frosting.

Vanilla Buttercream

  1. With the paddle attachment and on medium-high speed, beat the butter until it is pale and fluffy.
  2. Lower the speed to low and slowly add in the powdered sugar, beating until fully combined.
  3. Add in the vanilla extract and heavy whipping cream and beat until fully combined.
  4. Once the cakes have fully cooled, place the first layer on a large plate or cake stand. Use an offset spatula to frost each layer, followed by a thin crumb coat.

Galaxy Decoration

  1. Repeat the steps for vanilla buttercream to make the buttercream for the decoarations, and then separate the frosting into thirds.
  2. Leave 1/3 of the frosting white and set it aside for emergency purposes (in case you color something too dark).
  3. Take 1/3 of the frosting and color half of it pink and the other half blue.
  4. Use the last 1/3 to make black. Mix in the black cocoa powder to the buttercream. The buttercream may get thicker so you can add in the last 1 Tbsp of heavy whipping cream here (start with 1/2 Tbsp and then add the rest if it's still not spreadable).
  5. Add black gel food coloring, until the color is nice and dark (it may not be PERFECTLY black).
  6. Place dabs of different color buttercream on the top and sides of the cake and use a cake spreader or an offset spatula to distribute the colors. 
  7. If you add too much black, just add more of the lighter colors on top and vise versa. Just keep spreading it around the edge of the cake until you like how it looks. Remember that the more you spread it, the more the colors will blend together.
  8. When your frosting is complete, take a small paint brush, dip it into your white gel food coloring and use your finger to spray it onto your cake.

Nutrition Information:



Serving Size:


Amount Per Serving: Calories: 1145Total Fat: 60gSaturated Fat: 31gTrans Fat: 0gUnsaturated Fat: 26gCholesterol: 184mgSodium: 307mgCarbohydrates: 147gFiber: 1gSugar: 121gProtein: 7g

Nutrition information may not be fully accurate.

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  1. I made the cake, added strawberry marmalade I made myself, and it turned beautifully!
    I did two layers and it was awesome with the buttercream and the strawberries jam as filling in between 🙂

  2. hi i would like to make this cake, but i dont know if i should make any adjustments to the recipe since i live at sea level exactly 108 feet above sea level. thank you very much in advance, I love your blog!

    • Hi Trista, definitely! Just separate the batter, add some gel food coloring and then marble it. Try not to overmix the batter too much when adding the food coloring though.

      • hi i would like to make this cake, but i dont know if i should make any adjustments to the recipe since i live at sea level exactly 108 feet above sea level. thank you very much in advance, I love your blog!

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