You won’t believe how easy it is to transform a 9×13 sheet cake into this delightful Rainbow Unicorn Cake with a colorful candy clay (modeling chocolate) mane and tail. When you cut into the cake you’ll reveal a swirl of rainbow coloring hiding inside.
Did you, your mom, or grandmother ever bake a birthday cake from the Baker’s Coconut Cut-Up Cake recipe booklet? Mine did! Back in the 1960’s and early 70’s those cakes were all the rage. You simply baked one 9X13 sheet cake or 2 square or round cakes then cut them into simple shapes before assembling them to look like a lion, butterfly, duck, giraffe, dog, etc.
The cakes were easy to frost and decorate and looked so cute. These cut-up cakes were popular before shaped cake pans were available and the designs were easy enough for any home cook to recreate.
I even made the butterfly cake to enter into a baking contest when I was in junior high. I lost to a carrot cake which at the time was devastating, but now as an adult I understand how my pretty butterfly made from a strawberry cake mix couldn’t compete with a homemade carrot cake. I loved it nonetheless.
The idea for this Rainbow Unicorn Cake cake came to me when I saw some of the cutest Unicorn Valentine’s Day boxes. As with most things I see, I immediately imagined how the boxes would look as a sweet treat and my mind went straight to those cut-up cakes that I loved so much as a child.
To make this unicorn, you don’t need a pattern, you simply bake the 9×13 inch cake, cut it in half and use one half for the unicorn’s body. Then you cut the remaining half in half again and use one part for the head. The final piece of cake is then cut into two legs. You’ll have enough cake left over to create the unicorn’s horn or just to enjoy a snack. I did the later.
I wanted the interior of my unicorn cake to be just as magical as the exterior so I created a tie-dye rainbow swirl cake out of a white cake mix.
To make a rainbow swirl cake, you divide the cake batter into 6 bowls and color one bowl red, another orange, yellow, green, blue, and purple. Then you pipe or drizzle layers of color into the pan.
If you don’t want to go through that much effort, a simple white cake would be just fine.
To cover my cake, I piped frosting using a #21 star tip all over my cake. It’s a fun way to decorate a cake like this, but you can simply frost the cake, if you prefer. I didn’t go through the effort of making homemade frosting because I really like using Wilton’s Ready to Use Icing. It has a great flavor, is bright white, and pipes really nicely.
Being I wanted my cake on a black background and I didn’t have a black board that was the right size I cut a cake cardboard to fit underneath my cake and set it on a table-sized black board. You can simply place your cake on a large cutting board, serving platter or cake board.
To decorate this colorful unicorn cake, I used candy clay (modeling chocolate). Candy clay looks like fondant but tastes like chocolate so I love adding it to my desserts. You can use fondant, if you prefer. but you’ll need to either let your pieces air dry for about 24 hours or add tylose powder so that your pieces are firm enough to handle. The ear needs to be firm enough to keep it’s shape without drooping over the side of the cake.
If you use candy clay, the candy should harden in about 10 minutes and be firm enough to add to your cake, which is another reason I like using it so much.
Do you know I wrote a book about candy clay? If you’ve not ever made candy clay, it’s a simple 2-ingredient recipe that can be cut, sculpted, and even extruded. You can use it to decorate cupcakes, cakes, cookies, pretzels, and more. My book, Candy Clay Creations, is the ultimate resource on the subject and I’ll walk you through the steps to decorate 17 adorably cute treats. See the details about the book, which is available in print or ebook format, here.
Now, let’s take a look at the video tutorial so you can make your own Rainbow Unicorn Cake.
Wouldn’t your kids just love having this cake for their birthday party?
You can find everything you need to make this cake from Amazon. I make a commission on any sales at no additional costs to you so thanks for using the links below.
- 1 white cake mix
- ingredients listed on box (egg whites oil, water)
- red, orange, yellow, green, blue, and purple food coloring
- 3-4 cups white frosting
- 2/3-3/4 cup pink frosting
- 3-4 ounces white candy clay
- edible gold luster dust
- 1/2 ounce pink candy clay
- 1 ounce black candy clay
- 1 ounce each of red, orange, yellow, green, blue, and purple candy clay
- Preheat oven to 350 degrees F.
- Spray a 9 inch by 13 inch cake pan with baking spray.
- Optionally, line the pan with parchment paper and spray the paper.
- Divide white cake batter into 6 bowls (about 3/4 cup in each).
- Color one bowl red, another orange, yellow, green, blue and purple.
- Pour batter into individual disposable pastry bags or large zip top bags.
- Snip off the tip of the bag and pipe squiggles of one color batter into the pan.
- Use about 1/3rd of the batter for the first layer.
- Continue piping squiggles of colors, layering the 6 colors a total of three times.
- Tap the pan on the counter a few times to level the cake batter and to remove any air bubbles.
- Bake according to instructions on the cake mix box.
- Remove cake and allow to cool completely.
- Invert cake onto a cutting board.
- Remove parchment paper if necessary.
- Cut cake in half so you have two 9 inch by 6 1/2 inch pieces.
- One piece will be the unicorn's body.
- Cut the other piece in half so you have two 6 1/2 by 4 1/2 inch pieces.
- One piece will be the unicorn's head.
- Cut two 2 inch by 3 inch pieces for the unicorn's legs.
- Discard or eat the remaining pieces.
- Assemble the cake by placing the 9 inch by 6 1/2 inch cake in the lower half of your cake board forming the unicorn's body.
- Set the 6 1/2 inch by 4 1/2 inch piece about 2 1/2 inches from the top edge of the larger cake forming the unicorn's head.
- Place the two leg pieces under the body piece about 3/4 of an inch from either edge.
- Spoon frosting into pastry bags fitted with #21 star tips.
- Pipe white stars over the large cake.
- Pipe stars over 3/4's of the head and legs, leaving room to pipe on pink hooves and a pink snout.
- Pinch off about 3 ounces of white modeling chocolate and form into a twisted unicorn horn.
- Brush with edible gold luster dust and attach to the cake near the right side of the top edge of the head.
- Roll the remaining white candy clay to about 3/16th inch thickness. Cut out an ear using a 1 1/2 inch wide by 2 1/2 inch long tear drop cookie cutter or a knife.
- Roll out the pink candy clay to about 1/16th inch thickness.
- Cut a smaller tear drop shape.
- Use a small dab of water to attach the pink teardrop to the center near the lower edge of the white teardrop to form the unicorn's ear.
- Set the ear aside to dry for about 10 minutes.
- Roll out the black candy clay and cut out a 2 1/4 inch circle then cut just a thin edge from around the circle to create a thin moon shaped eye.
- Cut a small 3/4 inch round out of the black and do the same creating a nose.
- Cut four small rectangles then shape them into teardrop shaped eyelashes.
- Roll the remaining black candy clay into a long thin log for the unicorn's mouth.
- Use a dab of frosting to attach the candy ear to the upper right corner of the unicorn's head.
- Press the eye onto the cake to the left below the ear.
- Then press the four eyelashes above the eye.
- Press the black log onto the pink frosting creating the unicorn's smile.
- Cut off any excess candy.
- Press the nose above the smile.
- Roll all the other colored candy clay pieces into 8 inch long logs.
- Press them all together in rainbow order: purple, blue, green, yellow, orange, and red.
- Cut the logs into one 3 inch side and one 5 inch side.
- Flatten the logs and roll them out to about 1/4 inch thickness.
- Shape the longer piece into a curved tail pinching together the left side.
- On the right side, cut the ends so that each color has a nice pointed shape.
- Cut the left edge of the other piece so that it's straight then cut the opposite side so that each color has a nice pointed shape.
- Attach the tail to the top corner on the right side of the unicorn's body and the mane to the right edge of the unicorn's head.
- To make your cake easier to remove from the pan, line it with parchment paper.
- To make your cake extra moist, swap out 1/4 cup of sour cream for 1/4 cup of water.
- Be sure to use egg whites not whole eggs so that your cake batter is bright white which will be easier to color blue and purple.
- Use Wilton Ready to Use Icing to frost your cake. It tastes great, is easy to pipe, and easy to color.
- Do not store the cake in the refrigerator once it has been decorated with the candy clay or the decorations will become moist and sticky.