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kombu onigiri thumbnail

Kombu Onigiri (Kelp "Tsukudani" Rice Ball)

  • Author: Yuto Omura
  • Total Time: 50 minutes
  • Yield: 5-6 rice balls 1x


How to make delicious Kombu Tsukudani Onigiri. Japanese kelp simmered in soy sauce, mirin and sugar than wrapped in perfectly cooked sticky white rice. 


  • 50-60g used kombu kelp (approx 1 sheet - 12g when dry)
  • 500ml water
  • 2 tbsp sake
  • 1 tsp rice vinegar
  • 1 tbsp brown sugar
  • 1 tbsp mirin
  • 2 tbsp soy sauce
  • 1/2 tbsp sesame seeds

For making the onigiri

  • 600g cooked rice (300g or 2 rice cups before cooking)
  • 1 bowl of ice cold water
  • 2 tsp salt
  • 5-6 pieces of nori cut to onigiri size (1 sheet of sushi nori will be enough for approx 4 onigiri)


Before starting, make sure your kombu is already rehydrated. If you don't have used kombu, you'll need to soak it for 24 hours before making tsukudani. 

Your rice can be cooking while you make the tsukudani. Use Japanese short grain white rice or sushi rice. You need the rice to be sticky so that it holds it shape. We recommend using a rice cooker or see how to cook Japanese rice on the stove here.

Making Kombu Tsukudani

  1. Cut the soft used kombu into thin strips. (About 3mm or 1/10 inch thick)
  2. Add the sliced kombu to a pan with 500ml water, 2 tbsp sake and 1 tsp vinegar.
  3. Turn the heat on medium and bring to a rolling boil.
  4. Lower the heat and leave to simmer until the water has reduced by a bit less than half. (This should take about 20 minutes or so.)
  5. Add 1 tbsp brown sugar and mix. 
  6. Pour in 1 tbsp mirin and 2 tbsp soy sauce. Mix well and turn the heat back up to medium.
  7. Bubble until liquid is reduced to nothing, the kombu should be black with a thick soy sauce glaze. 
  8. Sprinkle in 1/2 tbsp of white sesame seeds and mix well. 

Shaping Onigiri

  1. Submerge your hands into ice cold water and hold them there for 15-20 seconds.
    dip your hands in the icy water for about 20 seconds
  2. Rub 1-2 pinches of salt over your palms.
    Rub salt over your palms
  3. Take a handful of cooked rice, lightly flatten it and push a dent into the middle. Place 1-2 tsp of kombu into the dent and fold the rice over.
    a moving image showing how to add fillings to onigiri rice balls
  4. Fold your palm and push the onigiri into the crease of your hand. Press and turn until you've formed a triangular shape.
    shaping a salted onigiri by hand
  5. Wrap the onigiri with a sheet of nori and enjoy! You can also place the kombu tsukudani on top of the rice ball for decoration.
    kombu onigiri in hand


If the kombu is too hard after step 8 then add more water (100ml at a time) and simmer until the liquid is gone. Repeat until texture is soft to your liking.

Store any left over kombu tsukudani in the fridge for 2-3 weeks. You can store leftover rice by letting it cool to room temperature and then storing in the freezer. 

  • Prep Time: 10 minutes
  • Cook Time: 40 minutes
  • Category: Rice
  • Method: Simmering
  • Cuisine: Japanese

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