Unagi-don (鰻丼), Japanese Style Grilled Freshwater Eel on rice

Unagi-don (鰻丼)


Unagi, or Anguilla japonica (日本鰻 ), is the name of the Japanese freshwater eel thats grilled over a charcoal fire whilst being coated in sweet soy sauce glaze, a style known as kabayaki (蒲焼). It’s always been one of my personal favourite dishes and it’s what I’d usually order in a restaurant when I feel like splurging. Seeing how expensive a bowl of Unagi with rice usually costs, I wanted to see if it where possible to make yourself and this post explores that. Other than it’s usual preparation method, Unagi is sometimes grilled with salt alone and served with wasabi, a style known as shioyaki (塩焼き).

Today, Unagi not only eaten all year round, but also throughout the entire world, so much that it has become a staple dish that one expects in any Japanese restaurant outside of Japan. This in return, has caused a decline in freshwater eel stocks to almost endangered levels. To counter this, the Unagi industry has switched to commercial farming of freshwater eel to meet the demand of various restaurants around the world. This however has not stemmed the problem of declining wild stocks as the current eel breeding technology is in it’s primitive stages and thus eel farming requires baby eels to be caught from the wild before being raised in captivity. While Unagi live their whole adult life in freshwater, they actually return to the sea to spawn and lay eggs.

Historically, Unagi used to be eaten on the midsummer day of the Ox (土用の丑の日), which falls on the 12th day before the start of autumn, as the protein and vitamin rich Unagi was said to provide strength and energy to workers for the coming year. Lake Hamana in Hamamatsu city, Shizuoka prefecture, is said to be where the best freshwater eel in Japan as the eel here is said to have superior flavour. As almost all of the eel eaten in Japan today is farmed, some farmers are trying to farm eel in a way that mimics wild in as close as possible as wild eel is suppose to have superior flavour due to its fat composition. Unagi naturally feel on plankton during the summer on order to grow as quickly as possible, before slowing down during the autumn in order to start storing fat. In the winter, these eels start to hibernate. These farmers try to mimic the seasons as close as possible in their farming ponds, even going the extra mile to store the Unagi in barrels which are placed in ice cold streams during the winter months to facilitate hibernation. This process is repeated over several seasonal cycles before the eels are harvested.


Unagi itself has an intrinsically rich and strong flavour, which is why the kabayaki style by which it is traditional prepared is so suitable for it as the mixture of caramelised sweet sauce pairs very well. The methods for preparing Unagi is so ingrained in Japanese culture that the recipe for making the sweet sauce is kept secret from restaurant to restaurant. While the base of the sauce is said to be made from a mixture of soy sauce, sake, mirin and sugar, the exact proportions vary from restaurant to restaurant, with the head of the restaurant only passing down the secret recipe through the family line. These particular restaurants specialize only in the preparation of Unagi alone and the pot of sauce bubbling away in the kitchen is their most prized possession. This is because the pot of sauce in each restaurant is never allowed to run dry, but is constantly topped up everyday when it starts running low. This causes the flavour to concentrate overtime and the remaining of the previous batches sauce are mixed into the new batch and allowed to slowly caramelise again. It is said some of these sauces have been kept going for over 5 generations and well over 100 years, never being allowed to run dry. In addition to this, some restaurants dip the entire skewers of Unagi into the pot of sauce between periodically while grilling, compared to brushing the sauce unto the Unagi on this grill. This means that some of the juice form the Unagi is mixed into the sauce everyday. Having been repeated everyday for over 100 years, causes each pot of Unagi sauce to develop its own individual complex flavour.

The method for preparing Unagi is also unique compared to other fish. In almost all other fish, the belly of the fish is slit open to remove the guts. In contrast, Unagi is prepared using the kejime method (活け締め), which involves, driving a meuchi (目打ち)  or nail directly through the hindbrain of a live eel, which causes immediate brain death as well as paralysis. This method is superior because it immediately causes the muscles in the eel to freeze, preventing any further use of energy in the body. If you were to kill the eel using any other method, the body of the eel would continue to trash about, causing the consumption of energy in the form of adenosine triphosphate (ATP). As the eel can no longer breath (because it’s dead), ATP is broken down through anaerobic glycolysis without oxygen, thus forming lactic acid which would give the eel a sour taste.

After dispatching the eel, the eel is filleted by cutting the down the backbone all the way down the entire length of the spine, splitting the eel open from top while leaving the belly untouched. This method is unique as it causes the belly to be positioned in the middle of the fillet, compared to conventional methods where the belly is cut in half. The innards are then scrapped away and the spine removed by inserting in knife underneath it and running it down the entire length of the eel. The eel is them skewered using bamboo skewers, ready for grilling.


The entire process of grilling Unagi is actually quite complicated. After being skewered, the Unagi fillets are grilled for a short period of time before being steamed. The initial grilling starts of the mallard reaction while the steaming that follows firms up the meat. The now firm Unagi fillet can then be deboned by hand. After deboning, the fillets is then dipped into the Unagi sauce and finished off on the grill before being served hot, with the skewers removed.

If we were to consider the preparation method for Unagi compared to other fish, it could be easily said that the Japanese overcook their Unagi as seafood usually only requires a short cooking time. However, this method of grilling, steaming and grilling actually creates a melt in your mouth texture. This is because the meat of Unagi is rather firm to start of with, and thus a fast cooking method such a pan searing would result in the Unagi becoming tough and rubbery. Furthermore the blood of the Unagi is poisonous if not cooked and thus this method of cooking ensures that the Unagi is safe to eat.

Grilled Unagi is more commonly served in a bowl, which is known as Unagi-don or Unadon (鰻丼) but can sometimes be served in a lacquered box, or Unaju (鰻重).


Unagi-don (鰻丼)

  • 1kg of salt
  • 500ml Water
  • 500ml Tamari Soy Sauce
  • 250g Granulated Sugar
  • 250ml Mirin
  • 200ml Sake
  • 2 Live Unagi, about 800g each
  1. Kill the 2 live Unagi by hitting each Unagi on the head with a mallet. Alternatively, if you have a nail or meuchi (目打ち) and hammer, drive the meuchi down the back of the head of the eel to kill it immediately.
  2. After dispatching the eel, clean the eel by rubbing it with the salt, one handful at a time before washing off with water. The goal here is to remove as much slime as possible from the eel using the salt. This process requires a lot of salt. Repeat several times until clean.
  3. Reattach the eel to the choping board if using a meuchi. Insert your filleting knife or debabocho (broad-bladed kitchen knife) right behind pectoral fin. and slide the knife along the entire spine to open the back.
  4. Remove innards by scrapping the knife along the eel.
  5. Remove the spine by inserting your knife under spine and running it between the spine and flesh.
  6. Place the fillets flat on the board and scrap the fillet gentle with the knife to remove any dirt.
  7. Wash gently with clean water.

    Red hot Charcoal Embers
  8. To make the sauce, combine the soy sauce, mirin, water, sake and sugar together in a pot and bring to a boil while stiring constantly to fully dissolve the sugar. Bring up to a vigorous boil to evaporate the alcohol from the sake.
  9. Reduce the sauce to your desired thickness. Add more sugar or soy sauce to taste.
  10. Cut the Unagi fillet into 4 equal portions and skewer each portion with 4 to 5 skewers.
  11. Place the skewers of Unagi over a charcoal grill for 5 to 6 minutes before rotating and grilling for another 5 to 6 minutes
  12. Place the skewers of Unagi in a steamer and steam for 15 minutes.
  13. Dip the skewers of Unagi in the sauce, grill on each side for 2 minutes.
  14. repeat 2 to 3 times.
  15. Remove skewers from the fillets and serve over steaming hot rice.



  1. It is possible to use this recipe starting with pre-filleted eels but I have yet to see it sold anywhere. The taste of fresh eel is still the best.
  2. Cleaning the eel requires a lot of salt and scrubing so it is best to wear gloves.
  3. Remember to cook the eel well as uncooked eel blood is poisonous.
  4. The innards of the eel should come out in one go if the eel is fresh.
  5. This recipe also works on catfishes.

3 thoughts on “Unagi-don (鰻丼), Japanese Style Grilled Freshwater Eel on rice

  1. Very well documented, thank you! Yes, unagi-don is extremely expensive. Our meal was a gift, so I truly appreciated the gesture.
    I read somewhere that the eel is held in place by piercing its eye (ouch!). Is that true?


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