These Rainbow Cake Push-Up Pops are something fun and whimsical and a bit unusual but they still have that perfect birthday cake flavor combo of butter cake and vanilla frosting. These are both just fun and delicious.
Gel food coloring in six rainbow colorsI used Americolor. Don’t use liquid coloring! It won’t be strong enough
24cake push-up pop containersavailable from Amazon or many other websites
For the Frosting:
10egg whitesroom temperature
1poundbuttersoft but still cool
1tbspvanilla bean paste or vanilla extract
To Make the Cake:
Line as many 9x13 pans as you have with parchment, and spray with nonstick cooking spray. (I actually used 9” round cake pans, but I ended up having to split the cakes in half so all 6 colors would fit in the pops. Splitting the thin cakes was tricky, and I think just making one ultra-thin layer of each color in a 9x13 would be easier.) Preheat your oven to 350 degrees Fahrenheit.
In a small bowl, combine the flour, baking powder, and salt, and sift together.
Place the butter and the granulated sugar in the bowl of a mixer and cream on medium-high until light and fluffy. Add the egg whites one at a time, beating well after each addition. Add the vanilla extract and mix it in.
With the mixer on low speed, add a third of the flour. Once it’s almost all incorporated, add half of the milk, then when that’s mixed in, add half of the remaining flour. Add the last of the milk, and once that’s gone, add the rest of the flour. Stop the mixer when it’s almost entirely mixed in, and do the rest by hand with a spatula, scraping the bottom and sides of the bowl to make sure everything’s incorporated.
Divide the batter into 6 even portions (this is easiest to do with a kitchen scale—weigh the total amount of batter, then divide by 6). Add enough gel food coloring to each portion to make a vibrant color—don’t be skimpy!
Pour the batter into the prepared pan(s) and bake until set in the middle, about 10 minutes. (It will be closer to 15 if you are using 9” rounds instead.) Let them cool for 10 minutes, then flip them out and let them cool completely. If you need to re-use the pans to bake off more colors, wash the pans and parchment/spray them, then repeat the process until all of your cake layers have been baked.
To Make the Frosting:
Combine the egg white and sugar in the metal bowl of a stand mixer. Bring an inch of water to a simmer in a saucepan that fits snugly on the bottom of your mixing bowl. Make sure that your water level is low enough that when you place the mixing bowl on top of the saucepan, the water doesn’t touch the bottom of the pan.
Whisk the egg whites/sugar over the simmering water bath until the whites are hot and the mixture has started to increase in volume and turn opaque. When you rub the egg whites between your fingers, the sugar should be completely dissolved and should not feel gritty at all.
Transfer the mixing bowl to the stand mixer and beat with a whisk attachment on medium-high speed until the whites are voluminous, shiny, and smooth. Beat them until they are not warm at all.
Add the soft but slightly cool butter to the whites a tablespoon at a time. As you continue to add the butter, the whites will deflate, and might even look curdled or broken. Don't worry! As long as you waited until the whites were cool, everything is fine. After all of the butter has been added, increase the mixer speed and beat for a few minutes, until the frosting smoothes out and comes together. Add the pinch of salt and vanilla extract and mix well. If for some reason it remains curdled, refrigerate the bowl for about 10 minutes, then beat on medium-high speed until it comes together.
To Assemble the Push-Up Pops:
Spread a thin layer of frosting on top of each cooled cake layer, about the same thickness as the cake itself. Refrigerate or freeze the cake layers until firm. Freezing is much faster, but requires a large amount of freezer space! (The purpose of this step is to create a very clean, even layer of frosting between each cake round. It can be skipped in favor of just piping in frosting, see Variations below.)
Once firm, use a round cutter slightly smaller in circumference than the push-up containers to cut 24 circles out of each color of cake/frosting. If you don’t have a cutter the right size, you can use the bottom plunger to cut out circles. It’s not as sharp as a metal cutter, so the cuts won’t be as clean, but it will still work.
If the frosting has softened during the cutting stage, return the cakes to the refrigerator or freezer until it is firm again.
Now begin assembly. Push the plunger up to the top of the container, and lay a cake/frosting round in it. Lower it slightly, and put a different color on top. Continue to lower the plunger and add cake layers until all six colors have been added. Push down to compact the layers and meld them together, if necessary.
After all of the pops are assembled, take the remaining buttercream and pipe a swirl on top of each one.
Variations: If you don’t care about perfectly smooth, even frosting rounds, assembly will go MUCH faster! Simply cut out cake rounds, and as you layer them in the container, use a piping bag to swirl a bit of frosting on top. It might be less even, but you won’t have to worry about keeping the cake chilled in order to be able to manhandle the frosting. Another timesaver is to only do a few colors per pop, instead of trying to squeeze in all six. If you do this, you can bake the cakes in 9” rounds and not have to worry about splitting the layers. Use only three colors per pop, with two frosting layers—this will also greatly reduce the amount of frosting you need. Win-win!