Kohakutou (Edible Crystal Candy) Recipe

Colorful gummy candies for decorating or snacking in style

By
Laurel Randolph
Photo of Laurel Randolph
Laurel Randolph
A fervid lover of the culinary arts and all things Instant Pot, Laurel has been writing about food for 10 years. One of her cookbooks was the #2 cookbook of 2017.
Learn about The Spruce Eats' Editorial Process
Updated on 12/31/22
Tested by
Bahareh Niati
Bahareh Niati
Tested by Bahareh Niati
Bahareh Niati is a professional food photographer and recipe developer. Baking and sweet treats are her favorites, and she shares her creations and love for baking on her blog Baking is Therapy.
Learn about The Spruce Eats' Editorial Process
Green edible crystal candies on a pink surface

The Spruce Eats / Bahareh Niati

Prep: 30 mins
Cook: 10 mins
Chill: 60 mins
Total: 100 mins
Servings: 30 servings
Yield: 1 (8-x 8-inch) pan

Kohakutou is a Japanese sweet that looks strikingly like a crystal or gemstone. The gummy candy can be used to decorate cakes, cupcakes, and other desserts, or simply enjoyed as a sweet treat. While the edible crystals look impressive, they're actually quite easy to make and only take a few ingredients.

These gummy candies are made of a mixture of sugar, water, and agar agar—a powdered substance made from red algae. When combined with liquid and heated, agar agar thickens and becomes jelly-like. We prefer the Telephone brand of agar agar as it produces a clear crystal candy and sets up nicely. Because kohakutou are made without gelatin, they're also vegan.

You can color your crystals all one shade, make a few different color crystals, or create swirls and patterns. Liquid food coloring works best, and you can add a candy flavoring of your choice. After setting up in the fridge, it's fun to cut and carve the candy into crystal shapes. While you can enjoy them right away, let them sit out for a few days to form a crust on the outside—they'll stay nice and soft on the inside.

“This recipe is very simple, with just a few ingredients! I really enjoyed cutting the jelly into different crystal shapes and loved how they all turned out unique. This can be a great family activity as you create the most beautiful candies, perfect for gifting. I used green apple flavoring and they turned out delicious!” —Bahareh Niati

Kohakutou: Edible Crystal Candy/Recipe Teseter Image
A Note From Our Recipe Tester

Ingredients

  • Cooking spray, for greasing

  • 4 teaspoons agar agar, preferably Telephone brand

  • 1 3/4 cups cool water

  • 3 cups granulated sugar

  • 1/4 teaspoon clear candy flavoring, optional

  • 3 to 6 drops liquid food coloring

Steps to Make It

  1. Gather the ingredients.

    kohakutou candy ingredients gathered

    The Spruce Eats / Bahareh Niati

  2. Prepare an 8-x 8-inch glass or metal square pan with smooth sides (or a few small pans to make different color crystals) by spraying lightly with cooking spray.

    four square metal baking dishes coated in oil

    The Spruce Eats / Bahareh Niati

  3. Stir to combine the agar agar and water in a medium saucepan. Let sit for 5 minutes.

    agar agar and water being stirred with spoon in a pot

    The Spruce Eats / Bahareh Niati

  4. Place the agar agar mixture over medium heat and bring to a boil, stirring constantly, until it has completely dissolved and the mixture thickens, 2 to 3 minutes.

    pot with agar agar and water over heat

    The Spruce Eats / Bahareh Niati

  5. Add the sugar and cook, stirring constantly, until it has completely dissolved and the mixture is thick and syrupy, about 3 minutes.

    sugar added to agar agar water mixture being stirred over heat

    The Spruce Eats / Bahareh Niati

  6. Remove the pan from the heat. Add the candy flavoring, if using, and stir to combine. If making a single color of crystals, add the food coloring to the pan and stir. To make multiple colors, work quickly to divide the mixture between bowls. Add food coloring to each bowl, stirring to combine.

    four bowls with agar agar sugar mixture, one with green food coloring, pink, purple, and jade food coloring and each with a spoon in bowl

    The Spruce Eats / Bahareh Niati

  7. Pour the mixture into the prepared pan(s). Refrigerate for 1 hour.

    kohakutou crystal candy mixtures poured into square metal pans, green, pink, dark green, and purple

    The Spruce Eats / Bahareh Niati

  8. Run a thin knife or offset spatula around the edges of the pan. Flip the pan over onto a parchment-lined baking sheet, then tap to dislodge the jelly. If the jelly is stubborn, cut it into chunks and remove those from the pan instead.

    set green agar agar candy square turned out from pan onto parchment lined sheet tray with offset spatula

    The Spruce Eats / Bahareh Niati

  9. Use a sharp paring knife to cut the jelly into crystal shapes, trimming as desired. The jelly will be firm but sticky. You can also tear the jelly to form jagged edges.

    kahakutou green gemstone candy cut from larger block into crystal shape with pairing knife on parchment lined sheet tray

    The Spruce Eats / Bahareh Niati

  10. Enjoy the crystals right away or let the crystals sit to form an outer crust (the inside will stay gummy).

    If enjoying later so that the crystals form this seal, spread the edible crystals onto the parchment-lined sheet and let sit at room temperature for 12 hours, then flip and let sit for 12 more hours or up to 3 days total before using and storing.

    kohakutou crystal candies cut out in pink purple, jade green and lime green spread out on lined baking sheet

    The Spruce Eats / Bahareh Niati

Decorating Tips

There are plenty of ways to customize these edible crystals:

  • Layers: create layers of color by mixing up to three colors in separate bowls. Add the first color to the prepared pan and place it in the fridge for 3 to 5 minutes, just until beginning to set up. Stir the remaining colors every minute or so to prevent forming a skin. Add the second color on top and chill again. Add the final color and chill for an hour before cutting into crystals.
  • Swirls: Create swirls of color by leaving the mixture clear or coloring it lightly with just a drop or two of food coloring. Add to the pan, then add several drops of food coloring spaced out on top. Use a skewer or toothpick to swirl it into the mixture, leaving a pattern.
  • Sparkle: Add a small amount of edible luster to the mixture or paint the edges of the cut crystals with edible luster paint or even gold leaf.

Recipe Variation

Play with the flavors of these edible crystal candies by using different candy flavorings. Citrus flavorings or oils work well, as do fun flavors like cotton candy. A clear flavoring works best since it won't interfere with the color.

How to Store

Once the crystals have formed a crust, move them to an airtight container and store at room temperature for up to a week. Do not freeze.

Nutrition Facts (per serving)
77 Calories
0g Fat
20g Carbs
0g Protein
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Nutrition Facts
Servings: 30
Amount per serving
Calories 77
% Daily Value*
Total Fat 0g 0%
Saturated Fat 0g 0%
Cholesterol 0mg 0%
Sodium 1mg 0%
Total Carbohydrate 20g 7%
Dietary Fiber 0g 0%
Total Sugars 20g
Protein 0g
Vitamin C 0mg 0%
Calcium 1mg 0%
Iron 0mg 0%
Potassium 1mg 0%
*The % Daily Value (DV) tells you how much a nutrient in a food serving contributes to a daily diet. 2,000 calories a day is used for general nutrition advice.
(Nutrition information is calculated using an ingredient database and should be considered an estimate.)