Have you've ever wondered if you can use your leftover kombu after making dashi? Well, the answer is, you can! In fact, you won't believe how delicious kombu can be until you try this recipe. This umami packed simmered kelp called "tsukudani" is one of the most popular onigiri fillings in Japan!
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Onigiri
An onigiri (おにぎり) is a popular Japanese rice ball, most commonly shaped into a triangle or cylinder and then wrapped with a thin sheet of dry seaweed called "nori".
They were also traditionally known as "omusubi" (お結び) or "nigirimeshi" (握り飯) but those words are not commonly used now, and if you do see them, it's more likely to be in writing rather than spoken.
Onigiri are eaten with hands (no chopsticks or spoon) and commonly seen in bento boxes. They're a popular option of lunch, it's kinda like a rice equivalent to a sandwich after all!
Onigiri Flavours
Onigiri can be made with just plain salted rice, but actually they come in all kinds of different flavours! Fish, meat, vegetables, you name it! The sky's the limit when it comes to onigiri. Not only are they highly customizable, but also portable and convenient for when you're on the go!
Here's a few popular flavours that you might see in Japan
- Salmon (鮭)
- Seasoned cod roe (辛子明太子)
- Hard cod roe (たらこ)
- Ume pickled plum (梅)
- Seasoned kombu seaweed (昆布)
- Tuna mayo (ツナマヨネーズ)
- Seasoned bonito flakes (おかか)
Today I'm going to show you how to make kombu onigiri, it's one of the top 5 onigiri flavours in Japan!
Kombu (昆布)
Kombu is a type of dried edible kelp and an essential ingredient in Japanese cooking. It's most common use is in "dashi", a soup stock that helps add umami and authentic Japanese flavour to dishes.
To make dashi, kombu is simply soaked until it's rehydrated and then heated up. I usually remove the kombu just before the water starts to boil as boiling kombu can release a bitter flavour into the dashi. Dashi is commonly used in miso soup, noodle broths and hot pot dishes.
After the kombu is removed from the dashi, there's no need to throw it away! You can use it to make this delicious tsukudani!
I use Hidaka Kombu for this recipe after using it to make dashi.
What is Tsukudani (佃煮)
Tsukudani is a traditional type of Japanese preserved food that has been simmered in a sweet and salty broth, most commonly made from soy sauce and sugars.
It can be made with fish, meat or vegetables, but I've gotta say that the umami from the kelp makes kombu tsukudani my favourite!
Since the broth is simmered down completely, the flavour is strong and concentrated. It's not really something you'd eat by itself, but it's the perfect accompaniment for rice, and the perfect onigiri filling!
Preparing Kombu for Tsukudani
It's best to use left over kombu for this dish. So after you've made dashi, don't throw the kombu away. You can either make tsukudani straight away, or save the kombu in the freezer for when you have time.
If you want to start with dried kombu, I recommend soaking it in water over night before use. The water will become dashi and you can store it in the fridge for another recipe.
The kombu takes a while to soften so I add 1 tsp of rice vinegar and 2 tbsp of sake to the water at the beginning. These additions help soften the kombu quickly.
In the case that you finish the recipe but the kombu is still a bit hard, you can return it to the pan, add more water and simmer it down until the water is gone. The tsukudani won't lose flavour because you'll evaporate the water down, repeat until you achieve the desired softness.
Kombu is the perfect onigiri filling or topping with rice! If you have leftover kombu tsukudani, you can keep it in the fridge for 2-3 weeks.
Print
Kombu Onigiri (Kelp "Tsukudani" Rice Ball)
- Total Time: 50 minutes
- Yield: 5-6 rice balls 1x
Description
How to make delicious Kombu Tsukudani Onigiri. Japanese kelp simmered in soy sauce, mirin and sugar than wrapped in perfectly cooked sticky white rice.
Ingredients
- 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
- ½ 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)
Instructions
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
- Cut the soft used kombu into thin strips. (About 3mm or 1/10 inch thick)
- Add the sliced kombu to a pan with 500ml water, 2 tbsp sake and 1 tsp vinegar.
- Turn the heat on medium and bring to a rolling boil.
- 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.)
- Add 1 tbsp brown sugar and mix.
- Pour in 1 tbsp mirin and 2 tbsp soy sauce. Mix well and turn the heat back up to medium.
- Bubble until liquid is reduced to nothing, the kombu should be black with a thick soy sauce glaze.
- Sprinkle in ½ tbsp of white sesame seeds and mix well.
Shaping Onigiri
- Submerge your hands into ice cold water and hold them there for 15-20 seconds.
- Rub 1-2 pinches of salt over your palms.
- 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.
- Fold your palm and push the onigiri into the crease of your hand. Press and turn until you've formed a triangular shape.
- 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.
Notes
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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Kiki
Thank you so much for this recipe! When I lived in NYC, onigiri from a local Japanese market was a frequent on-the-go snack for me, and kombu was my favorite onigiri filling. Now that I live in rural WV, it is hard to find prepared tsukudani, even on trips to Asian supermarkets in bigger cities. This recipe nails the flavor perfectly, and it can be made with ingredients that are not too hard to find (or that can be ordered online). I've made it several times now, most recently in a bigger quantity - it keeps quite well in the fridge. You are a lifesaver - thank you!
★★★★★
Yuto Omura
Hi Kiki,
I'm so happy to hear you're enjoying the recipe and can now enjoy kombu onigiri anytime! I've never seen kombu onigiri outside of Japan, I'm sure you can only find it in very specific Japanese supermarkets. Thank you for your kind rating 🙂