Japanese Eel Soup: A Clear, Savory Unagi Broth Recipe

Japanese eel soup is a light, savory broth made here with grilled unagi, dashi, mushrooms, tofu, and fresh greens. This home-style version balances the eel’s sweet glaze with a clean, gently seasoned soup, and it comes together quickly with ready-to-eat grilled eel.

Japanese soups vary by region and household, so this is one practical interpretation rather than a claim to a single definitive style. It is different from kimosui, a traditional clear soup commonly made with eel liver; this recipe uses familiar, fully cooked grilled eel for an easier meal.

Ingredients

6 cups (1.4 L) dashi broth, homemade or prepared
12 oz (340 g) fully cooked Japanese grilled eel, or unagi kabayaki, thawed if frozen
4 oz (115 g) fresh shiitake mushrooms, stems removed and caps thinly sliced
7 oz (200 g) soft or medium-firm tofu, cut into ¾-inch (2 cm) cubes
2 tablespoons (30 ml) Japanese soy sauce
1 tablespoon (15 ml) mirin
1 tablespoon (15 ml) sake, optional
1 teaspoon (5 ml) finely grated fresh ginger
2 cups (60 g) baby spinach or mizuna, loosely packed
2 scallions, about 2 oz (55 g), thinly sliced
1 tablespoon (3 g) chopped mitsuba or flat-leaf parsley
1 teaspoon (2 g) toasted sesame seeds, optional
1 teaspoon (5 ml) toasted sesame oil, optional

Instructions

Prepare the eel and vegetables. If the eel is frozen, thaw it in the refrigerator according to the package directions. Cut it into four portions or bite-size pieces and set aside. Slice the shiitake caps, cube the tofu, grate the ginger, and wash and drain the spinach or mizuna. Slice the scallions and chop the mitsuba. Keep the eel separate from the raw garnishes so it is easy to portion after heating.
Warm and season the dashi. Pour the dashi into a medium pot and set it over medium heat. Add the soy sauce, mirin, optional sake, and ginger. Bring the liquid to a gentle simmer, not a rolling boil. Taste a spoonful before adding salt: dashi and eel glaze vary in saltiness, so the broth may need no extra seasoning. If it tastes too strong, add a little water; if it is very mild, add soy sauce a teaspoon at a time.
Cook the mushrooms. Add the sliced shiitake to the simmering broth and cook for 5 minutes, stirring once or twice. The slices should soften while still holding their shape. Keep the surface at a quiet simmer; a hard boil can make the broth cloudy and break up delicate tofu later. If using dried shiitake instead, rehydrate them beforehand as directed on the package, slice them, and add a little of their strained soaking liquid only if it tastes clean and pleasant.
Add the tofu. Lower the tofu cubes carefully into the broth and simmer for 2 minutes. Move them gently with a spoon rather than stirring vigorously. Soft tofu is delicate and can crumble, but it adds a silky texture; medium-firm tofu is easier to handle if you prefer distinct cubes.
Heat the eel safely. Add the fully cooked eel pieces and warm them gently for about 4 minutes, turning once if needed so they heat evenly. Avoid prolonged boiling, which can make the eel tough and cause its sweet sauce to overpower the dashi. Because this recipe reheats cooked seafood, check the center of the thickest piece with a food thermometer: USDA FSIS guidance for reheated leftovers is 165°F (74°C). Follow any stricter heating instructions on the eel package.
Finish with greens and serve. Stir in the spinach or mizuna and cook for about 1 minute, just until wilted but still bright. Taste the broth once more and adjust with a splash of water or a small amount of soy sauce. Ladle broth, mushrooms, and tofu into four warmed bowls, then divide the eel among them. Top with scallions and mitsuba. Add sesame seeds or a few drops of sesame oil if desired, and serve promptly while the eel and soup are hot.

Tips

Choose the right eel. Look for fully cooked unagi kabayaki, often sold frozen or refrigerated in a vacuum pack at Japanese or other Asian grocery stores. It is usually brushed with a sweet soy-based glaze. If you can only find plain cooked eel, this soup will be less sweet; taste the broth and add a little extra mirin if you want a rounder flavor. Do not use raw eel as a direct substitute without a suitable preparation and cooking method.
Use a sensible dashi substitute. Kombu-and-bonito dashi gives the soup its characteristic savory, oceanic base. Instant dashi granules are a convenient substitute; mix them with water following the packet’s ratio, then taste before adding soy sauce because some mixes are already salty. For a vegetarian version, use kombu-and-shiitake dashi or a mild vegetable broth. Vegetable broth makes the result less traditionally Japanese in flavor, so keep it lightly seasoned.
Keep the broth gentle. A rolling boil can cloud a clear soup, damage tofu, and make reheated eel chewy. Bring the liquid only to a quiet simmer, and add the eel near the end. The eel’s glaze will dissolve gradually into the broth, so wipe away excessive sauce if you want a clearer, less sweet soup.
Season in stages. Different brands of eel, dashi, soy sauce, and instant stock have different salt levels. Start with the listed soy sauce, then taste after the eel has warmed. Add more only in small amounts. If the broth becomes too salty, dilute it with hot water or unsalted dashi rather than adding sugar.

Serving Suggestions

Serve the soup as a light main course with a bowl of steamed Japanese short-grain rice. The rice is especially useful for catching the savory broth and balancing the eel’s sweet glaze. For a more substantial meal, add a small plate of quick-pickled cucumber, blanched greens with sesame, or edamame. These sides provide contrast without competing with the soup’s delicate dashi flavor.

For a simple presentation, arrange the eel on top rather than burying it under the tofu and vegetables. This keeps the glaze visible and makes each bowl feel generous. Offer extra sliced scallions, mitsuba, toasted sesame seeds, or shichimi togarashi at the table. Add chili seasoning sparingly: its heat can quickly dominate the mild broth. If serving the soup as a first course, use smaller bowls and follow it with rice, grilled vegetables, or another Japanese-style dish.

Variations

Make it vegetarian. Leave out the eel and use kombu-and-shiitake dashi. Add another 4 oz (115 g) of mushrooms, or include a handful of sliced napa cabbage. The result will not have the same glazed, smoky richness, but the mushroom broth and tofu make a satisfying clear soup. A few drops of toasted sesame oil can add depth; use it lightly so the dashi remains noticeable.

Swap the greens. Mizuna and spinach cook quickly, but watercress, thinly sliced napa cabbage, or tender bok choy leaves also work. Add sturdier leaves earlier and tender leaves at the end. If using bok choy, separate the stems from the leaves and simmer the sliced stems with the mushrooms for several minutes before adding the leaves.

Make it heartier. Add 4 oz (115 g) cooked udon noodles to each bowl before ladling in the soup, or serve a larger portion of rice alongside. For a noodle version, increase the dashi to 7 cups (1.65 L) and taste the finished broth before serving, since noodles can absorb some liquid. Keep the eel portions on top so they warm without getting lost among the noodles.

Adjust the sweetness. Kabayaki glaze is already sweet, and some prepared eel comes with extra sauce. For a more restrained broth, remove visible excess glaze before adding the eel and reduce the mirin to 2 teaspoons (10 ml). For a sweeter, richer bowl, stir in up to 1 teaspoon (5 ml) of the eel’s sauce after tasting; add it gradually, since too much can make the dashi taste heavy.

Storage and Reheating

For the best texture, serve this soup soon after cooking. If you have leftovers, refrigerate them within 2 hours in a shallow, airtight container. They keep for 3 to 4 days in the refrigerator. If possible, store the eel separately from the broth, tofu, and greens; separate storage helps the eel keep its texture and prevents its glaze from sweetening the entire pot as it sits.

Reheat only the portion you plan to eat. Warm the broth and solids gently in a covered saucepan over medium-low heat, stirring carefully, until hot throughout. Check that reheated eel reaches 165°F (74°C), the USDA FSIS target for reheated leftovers. Avoid repeatedly cooling and reheating the same batch. The greens will soften and the broth may become slightly cloudy after storage, but that is a texture change rather than a reason to boil it hard.

Freezing is possible for up to 2 months, though tofu can become spongy and leafy greens may turn limp after thawing. For better results, freeze the broth with mushrooms and add fresh tofu, greens, and eel when you reheat it. Thaw frozen soup in the refrigerator, then bring it to a safe temperature on the stove; do not thaw it for an extended time at room temperature.

Frequently Asked Questions

What is Japanese eel soup called? There is not one name for every soup made with eel. Kimosui is a recognized Japanese clear soup traditionally made with eel liver and often served with eel dishes, while this recipe is a home-style dashi soup with grilled eel. Menus and household recipes can use different preparations, so the ingredients matter more than assuming every eel soup is the same dish.

Can I use frozen unagi? Yes. Many packages of grilled unagi kabayaki are sold frozen and are already cooked. Thaw it in the refrigerator according to the package directions, then warm it gently in the soup. Check the label for any specific heating instructions and make sure the thickest piece reaches 165°F (74°C) when reheating, as directed for leftovers.

Can I make this without dashi? You can use a mild vegetable broth or water with instant dashi, but the flavor will change. Dashi is what gives the soup its characteristic savory Japanese profile. If using vegetable broth, choose a low-sodium one and season slowly; strong herbs or a heavily salted stock can overwhelm the eel. Kombu-and-shiitake broth is a good option if you want a vegetarian soup.

Is eel soup supposed to taste sweet? It can have a gentle sweetness because kabayaki eel is brushed with a sweet soy glaze, but the broth should still taste savory and light. The sweetness depends on the eel brand and how much sauce is on it. Wipe off excess glaze, reduce or omit the mirin, and adjust the broth after the eel has warmed if you prefer a less sweet bowl.

Can I prepare the soup ahead? You can slice the vegetables and prepare the dashi a day ahead, keeping them covered in the refrigerator. For the best texture, cook the mushrooms and tofu, then warm the eel and wilt the greens shortly before serving. If you cook the full soup in advance, cool and refrigerate it promptly, then reheat each portion thoroughly to 165°F (74°C).

What should I look for in a Japanese eel soup video? A useful demonstration should show the broth at a gentle simmer, the eel being added near the end, and the finished soup being portioned without breaking up the tofu. Check whether the eel is already cooked or raw, because the handling and cooking requirements differ. This recipe assumes fully cooked kabayaki eel and includes a thermometer check for safe reheating.

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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes

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