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tutorial: rainbow kohakutou edible jelly crystals cake

Today I combine two loves = Rainbow Edible Jelly Crystals + Cake.

For the written step by step, carry forward! If you'd like the video tutorial, click this image:

RoxStarBakes Rainbow Kohakutou Edible Jelly Crystal Cake

My tried and tested vanilla cake is fluffy, moist, and delicious. If you don’t want to go the made from scratch route, use boxed cake! No biggie. Since something had to be different about this project, I decided to make a 5” square cake. It was so fun!

  • How to make a lilac multicolor square cake

  • How to make rainbow edible jelly crystal kohakutou

  • How to decorate a cake with edible jelly crystals ;)

Most asked questions:

  • Why should I love Kohakutou? Kohakutou Jelly Crystsals are an awesome alternative to rock candy because they taste delicious, are gummy textured on the inside and get crunchy on the outside when they have had time to dry. The textures are crazy good!

  • What’s awesome about this cake? I get a lot of asks for inspiration using my edible jelly crystals (Japanese kohakutou recipe) and for surprise inside cakes. This is both!

  • Do you have a suggestion for a low sugar filling? Yes! A couple years back I made a chia jam recipe that has no refined sugar because I was getting a lot of asks for one. I made it in strawberry, raspberry, blueberry, mango and pineapple.

  • Can I make the cake in advance of decorating? Yes! In fact, I recommend you make them a day or two before, wrap them really well and keep them frozen. The cakes will stay moist and there’s something about this process that makes the cakes tastier.

  • How many people does this cake serve? 10-12 people


Kohakutou crystals

Swiss meringue buttercream

Vanilla cake


How to make Kohakutou Rainbow Edible Crystals:

Step 1 – make 1 batch of this crystal mixture. Divide the mixture into 6 or 7 bowls and then color these rainbow inspired (one pink, red, orange, yellow, green, blue and purple) with gel food paste. Once you’ve made these individual colors, pour the crystal mixture into a large glass baking tray (I’m pretty sure that’s what’s that’s called). Let sit in the fridge for 1 hour.

How to shape the crystals:

Step 2 – forming the crystals. Loosen the firmed Kohakutou onto a silicon mat or piece of parchment paper. If it’s tougher to get out, cut from one corner to the opposite corner and turn over onto parchment paper or silicon mat. From here, cut smaller squares and start to form crystals. Carve long pieces so when they’re sticking out of the cake they appear as if they’re bursting out! Place finished crystals on a baking sheet and cover with plastic wrap. Set in fridge until ready to place on cake.

  • Tip: For planning, you can do this 2 days in advance.

RoxStarBakes Rainbow Kohakutou Edible Jelly Crystal Cake
RoxStarBakes Rainbow Kohakutou Edible Jelly Crystal Cake
RoxStarBakes Rainbow Kohakutou Edible Jelly Crystal Cake

How to make Swiss meringue buttercream:

Step 3 – make 1 batch of this buttercream. I thought that these rainbow crystals would look the tastiest and stand out best against white frosting so I left it plain.

· Tip: This can be made the day before.

How to make lilac cake batter (can be done 2 days before and frozen):

Step 4 – make vanilla cake batter.

Step 5 – mixing the batter into colors. Add a little batter into a bowl. Add lilac color into the bowl. Mix mix mix! Then distribute the rest of the batter and incorporate thoroughly.

  • Tip: I mix the batter in stages to get the most even color distribution.

  • Tip: Remember it’s easier to add than remove color! So be conservative.

Step 6 – distributing the batter for baking. Distribute the batter across 3, 5-inch cake pans that are lined with parchment paper (this is clearly demonstrated in my video). Use a knife or angled spatula to pull the batter to the sides (score the batter). Then bang the batter to release any extra-large air bubbles and also fill in the edges. Bake for 28-30 minutes or use a toothpick to see if the baking is complete - there should be about 5 crumbs.

  • Tip: It’s best not to grease the sides so the cake batter can climb the sides of the pan as it bakes. I love tall and fluffy cakes!

  • Tip: Loosen the edges with a thin knife or angled spatula and place on a cooling rack to cool completely.

  • Tip: Dust your chocolate chip cookies with 1-2 tablespoons of flour so the chocolate chips don’t sink to the bottom and settle when folded into the batter and baked.

  • Tip: Make sure the cakes are cooled before releasing and decorating.

Step 7 – level the cakes. Once cooled, level the cakes if necessary (varies by oven). I use a bread knife but there is no one way to do this.

How to assemble the cake:

Step 8 – filling and crumb coating. To assemble the cake, place 1 cake layer on a cake stand and adhere with buttercream. Pipe an outline around the edge of the cake and fill it in with frosting. Smooth it out using an angled spatula. Top with a second cake layer and press firmly so the cake adheres. Check the top and sides to make sure the cake is level. Continue building until the all layers are placed. Use the white frosting to crumb coat the cake by spreading on a thin layer of frosting and then scraping the excess away. It’s a thin layer of frosting to lock in the moisture and capture the crumbs. I use a cutting board to support the cake as I crumb coat to make it a little easier. Then place in the refrigerator for 15-30 minutes.

  • Tip: You can use a level to ensure the cake is leveled.

  • Tip: Make sure the cake is completely cold.

  • Tip: Make sure to press gently between each cake layer to ensure the cake is secure.

RoxStarBakes Rainbow Kohakutou Edible Jelly Crystal Cake
RoxStarBakes Rainbow Kohakutou Edible Jelly Crystal Cake
RoxStarBakes Rainbow Kohakutou Edible Jelly Crystal Cake

Step 9 – frosting the cake. Add some frosting to the top of the cake. To get sharp corners of the cake, I place an acrylic square wrapped in saran wrap (a cake board works too) on top of the cake and then continue adding frosting to the cake. I find it’s quickest to use a piping bag for the distribution. Tighten the frosting with an angled spatula. Then use a cake scraper to smooth and remove any excess.

RoxStarBakes Rainbow Kohakutou Edible Jelly Crystal Cake
RoxStarBakes Rainbow Kohakutou Edible Jelly Crystal Cake

Step 10 – carving the cake to add the crystals. Decide which side is going to be the front of your cake. Create a slit from the cake from the top right side of the cake to the bottom left side of the cake. Add some buttercream back in and add the large crystals. Place the crystals so they are firm and secure, using dibs and dabs of frosting with an angled spatula to hold everything in place Using smaller crystals, fill in any gaps.

  • Tip: The cake is fresh for three days and can be kept in the fridge. Allow to get to room temperature before serving for best flavor.

  • Tip: Once you’ve sliced the cake to enjoy, if you place plastic wrap where the slice is removed, it keeps the cake fresher and prevents drying.

RoxStarBakes Rainbow Kohakutou Edible Jelly Crystal Cake
RoxStarBakes Rainbow Kohakutou Edible Jelly Crystal Cake
RoxStarBakes Rainbow Kohakutou Edible Jelly Crystal Cake

Rainbow crystals cake success!!!


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