How to Decorate a Store Bought Cake so you dont Have to Bake!

I love creating fun, themed parties for my daughters birthdays. A big part of the party theme is the cake, but with all the other planning that goes into a party, I stopped actually baking the cakes and starting buying cakes from Costco and re-decorating them. By doing it this way I know the cake will taste delicious, but I still get to be a part of decorating something more personalized for my kids. Below is the basic idea of how I do it. There are affiliate links at the bottom of the post to most of the items I used.

Usually, I gently scrape the excess frosting off the cake and redecorate with my own frosting and party-themed style. In the picture below, I bought the round chocolate fudge cake (the one with all the chocolate shavings on the top) and added my own bright frosting, sprinkles, and LOL Doll decorations to the top. Pro tip: when you buy a cake with chocolate shavings on top, you get to eat them while removing them from the cake. Yum!

This year, however, the round fudge cake was not available. So I decided to buy a plain sheet cake and try to wing it. It worked out surprisingly well! Everyone around here loves Costcos chocolate sheet cake and it wasnt as difficult for me to rework as I thought it would be. Take a look at how I did it below for my daughters mermaid cake!

I started with this plain chocolate sheet cake. I used a bench scraper to gently scrape off the excess frosting. Then, because I wanted to make a round cake, I needed to cut my cake into circles. (I know, I could have made my life easier and just decorated the cake as is, but wheres the challenge in that? Also, my daughter had seen some baking shows and really wanted a tall layer cake.) I experimented with a few different sized round bowls to see which size would get me three layers. You can see in the picture above the outlines of the bowl on the frosting.

Next, I cut three circles out of the cake. I used my bowl as my guide so they would all be perfectly round and the same size. This did leave a bit of leftover cake which I served to some of my guests who didnt want as much frosting and I also froze some to bring out one cold February night when we all want a treat at home.

I gently stacked the layers as I cut them out. I didnt put anything in between them, but I did use large straws as dowels for stability. I pushed three straws down through all three layers. I needed to cut the tops of the straws so they didnt show.

Finally, I added a quick crumb coat from the frosting I scraped off at the beginning before putting the cake into the refrigerator until the next morning. This step was the hardest, I really needed to be careful to not pull off any of the cake. On the morning of the party, I quickly whipped up a batch of buttercream frosting and tinted it teal, pink and purple. Decorated my cake in a fun Mermaid theme and had a great party!

For the cake details, I bought white and blue pearlized sprinkles to be water bubbles. For the seaweed, I bought Haribo Sour Streamers and cut the green ones into long pointed strips, then pushed them into the frosting on the bottom. I then twisted them and pushed them into the frosting on the top. They held very well and of course, all the kids wanted a piece with seaweed on it!

And what mermaid cake would be complete without a mermaid? I bought this Schleich Mermaid figure from Amazon and placed it on top with some extra frosting details and a candle. While obviously not a professional cake, it was perfect for my six year old and perfect for me because I didnt have to bake anything!

Items in this post:

Mermaid on top of cake:
Similar cake turntable:
White Bubble Sprinkles:
Blue Bubble Sprinkles:
Seaweed Haribo Sour Streamers:
Similiar LOL Doll Cake Sprinkle Mix:
LOL Doll Series on Cake:

*affiliate links