Galaxy-Glazed Rainbow Cake


For my daughter’s seventh birthday she declared that she wanted a Parry Gripp-themed party. Who is Parry Gripp? Try typing it in as a search term on YouTube and go down the rabbit hole of playlists…

The short answer is that he writes weird songs, most of which appear to be aimed at kids, with accompanying bizarre animated music videos. Current favorites in this house include “Neon Pegasus,” “Space Unicorn,” and “Pancake Robot.” There are actually a ton of food-related songs, which we used as inspiration for our party menu, but one thing my kid was adamant about was that she wanted a galaxy-mirror-glazed cake, which would relate to both Neon Pegasus and Space Unicorn. I’m not sure where she even found out about mirror-glazed cakes, but hey, the apple doesn’t fall far from the tree!

We decided to make the inside with rainbow layers (because Space Unicorn delivers the rainbows all around the world), which of course led to a giant cake because of the need for six different-colored layers inside. I used a double batch of the standard White Almond Sour Cream cake recipe that’s all over the internet— it’s based on a box of white cake mix that’s had extra ingredients added (I omitted the almond flavoring and used milk instead of water), and it baked up nicely.


Once the 9″ cake layers were baked I stacked and iced them using the upside-down frosting technique, which makes for some really nice sharp edges and smooth sides. I used a level between each layer to make sure everything was nice and even. I chilled it overnight, flipped it over, and then let it spend almost 2 hours in the freezer before pouring the glaze over it.

Honestly, I relied most heavily on this tutorial for how to glaze the cake in the galaxy design. I highly recommend it.

The glaze (recipe and tips below)

Mirror Glaze (adapted from Also The Crumbs Please)

(I doubled this recipe to make plenty of glaze for my gigantic cake)

  • 3/4 cup cold water (180ml)
  • 7 + 1/2 tsp powdered gelatin (35g)
  • 12 oz. white chocolate (350g)
  • 1 1/2 cups granulated white sugar (300g)
  • 3/8 cup water (90ml)
  • 3/4 cup light corn syrup (245g)
  • 3/4 cup sweetened condensed milk (230g)
  1. Add ¾ cup of water and gelatin in a small bowl and stir to combine. Let bloom for about 10 minutes.

  2. Place chopped white chocolate in a large bowl and set aside.

  3. In a small saucepan heat the sugar, 3/8 cup water, and corn syrup over medium heat. Bring to a boil and simmer for about 2-3 minutes. Remove from stove and stir in bloomed gelatin and condensed milk until combined. Pour over the white chocolate, cover with a towel, and let stand for about 2 minutes to let the chocolate melt.

  4. Mix with a handheld immersion blender until smooth. Pour through a mesh strainer to remove any lumps.

    To glaze cake:

    5. Set frozen cake on top of an overturned bowl on a parchment- or foil-lined baking sheet. You need the glaze to be able to drip off easily.

    6. Separate glaze into 5 bowls– two large and three small. Dye the two larger bowls of glaze dark and medium blue, respectively. Dye the smaller bowls pink, purple, and bright blue. Allow the glaze to cool to 90 degrees F, stirring frequently to keep the heat distributed evenly.

    7. Pour the medium blue glaze into the bowl of dark blue glaze and run a butter knife through it to swirl slightly, making sure the medium blue makes it all the way to the bottom of the bowl. Pour over the top of the cake, starting at the center and allowing excess glaze to run over the edges.

    8. Pour small stripes of the other three glazes over the still-wet cake. Using a large spatula, gently spread the glazes over the top of the cake to blend.

    9. Dip a clean, dry paintbrush into pure white food coloring and use your finger to spatter tiny dots over the surface of the cake. Add edible glitter as desired.


  • It takes a while for this glaze to cool down, so I would recommend putting your chilled cake in the freezer before you start to assemble your glaze ingredients. By the time your glaze is cooked, mixed, and cooled, your cake should be firm enough to glaze.
  • Most of the recipes online highly recommend using good-quality white chocolate rather than white chocolate chips, since chips rarely use real cocoa butter. I decided that since I was making a double batch of glaze, using real white chocolate would cost a fortune that I wasn’t willing to spend, so I used Ghirardelli white chocolate chips instead. They worked fine.
  • Everyone says to let the glaze cool to 90 degrees F before pouring, but I found it ever-so-slightly too thick at that temperature. I think I would’ve preferred it to be just a tiny bit warmer so it would be runnier.
  • That being said, I’m sure that part of my trouble getting the glaze to run all the way down the sides was due to the height of my cake, which was admittedly pretty tall. Having to travel down several inches of cold cake probably contributed to the cooling of the glaze during the pouring process. If I’d been using a more normal-sized mousse cake or small individual desserts, it’s possible the glaze would’ve been fine at 90 degrees.
  • This stuff gets really rubbery when it sets– make sure that you either wipe off any extra drips at the bottom of the cake while they’re still warm, or be prepared to use scissors to snip them off when they’re cool. A regular knife won’t be sufficient. I will also note that for me, the rubberiness was compounded because the cooler temperature made it set into a thicker skin that didn’t cut cleanly with a knife. I ended up having to peel the glaze off before I was able to cut nice slices from the cake. I’m sure that if it had been warmer it would’ve formed a thinner skin, so keep that in mind.

2 thoughts on “Galaxy-Glazed Rainbow Cake

  1. Pingback: Marbled Cake Pops | It's All Frosting...

  2. Pingback: Strawberry-Champagne Entremet | It's All Frosting...

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