Japanese Green Onion Soup: A Simple Miso-Free Recipe

Japanese green onion soup is a light, savory soup built around dashi, miso, and tender green onions, often with tofu and wakame seaweed. This version is easy to make at home and balances the onions’ fresh bite with a gently salty broth; ingredients and ratios vary among cooks and households.

Ingredients

6 cups (1.42 L) water
1 tablespoon (about 9 g) instant dashi granules, or the amount specified on the package for 6 cups of broth
6 medium green onions (about 90 g), or 2 Japanese negi (about 300 g), trimmed
1 tablespoon (5 g) dried wakame
8 ounces (225 g) soft or medium-firm tofu, cut into ½-inch (1.25 cm) cubes
¼ cup (60 g) white or awase miso
1 tablespoon (15 ml) mirin, optional
1 teaspoon (5 ml) soy sauce, optional
1 teaspoon (3 g) toasted sesame seeds, for serving, optional

Instructions

Prepare the vegetables and wakame. Rinse the green onions and pat them dry. Slice them thinly on a diagonal, keeping the white and pale-green pieces separate from the darker green tops. Put the dried wakame in a small bowl, cover it with cool water, and soak for 5 minutes while you prepare the other ingredients. Drain and gently squeeze out excess water; it will expand as it rehydrates. Cut the tofu into small, even cubes so it warms through quickly without breaking apart.
Make the dashi base. Add the water to a medium saucepan and stir in the dashi granules. Bring the liquid to a gentle simmer over medium heat, stirring so the granules dissolve. Follow the package amount if it differs from the quantity listed, since brands vary in strength and saltiness. If you are using prepared dashi instead, use 6 cups (1.42 L) in place of the water and granules.
Soften the onion whites. Add the sliced white and pale-green onion pieces to the simmering broth. Cook gently for 5 minutes, until they are softened but not falling apart. Keep the liquid at a simmer rather than a rolling boil; a hard boil can make the broth cloudy and can leave the onion with a harsher, less delicate flavor.
Add the tofu and wakame. Slide the tofu cubes and drained wakame into the saucepan. Simmer for 3 minutes, stirring carefully once or twice so the tofu stays in neat pieces. The goal is to heat the tofu through and let the wakame season the broth lightly, not to cook the ingredients until they lose their texture.
Stir in the miso off the heat. Turn off the burner. Put the miso in a small bowl, ladle in about ½ cup (120 ml) of hot broth, and whisk or stir until smooth. Pour this mixture back into the pan. Add the mirin and soy sauce, if using, then stir gently. Taste before adding any extra seasoning; dashi granules, miso, and soy sauce can all contribute salt.
Warm and finish the soup. Set the saucepan over low heat for 1 to 2 minutes, stirring gently, until the soup is hot and steaming. Do not let it boil after adding the miso, because high heat can dull its aroma and make the broth less smooth. Divide the soup among four bowls, add the sliced green onion tops, and finish with sesame seeds if you like. Serve promptly.

Tips

Choose an onion that suits your market. Japanese negi are long, thick onions with a mild flavor and tender white stalks. They can be hard to find outside Japanese or well-stocked Asian grocery stores. Ordinary green onions or scallions work well; use both the white and green sections, and add the dark green tops near the end so they stay bright. Leeks can stand in for the white portion, but their flavor is sweeter and more mellow.
Know which dashi you are buying. Instant dashi granules are a convenient shortcut, while homemade dashi is often made by steeping kombu (dried kelp) and katsuobushi (dried bonito flakes) in water. If those traditional ingredients are unavailable, granules are a practical substitute and give a similar savory base, though the aroma and depth may differ. Some dashi products contain fish, so check the label if you need a vegetarian soup.
Mix miso separately before adding it. Miso tends to clump if it is dropped straight into the pan. Loosening it in a small ladleful of broth gives you a smooth soup without straining or vigorous whisking around the tofu. White miso is mild and slightly sweet; awase miso, a blend of miso types, tastes a little fuller. Both work, but the finished soup will vary in saltiness and intensity.
Season gradually and avoid overcooking. Taste the broth after the miso has been mixed in, then decide whether the optional soy sauce is needed. Keep the tofu cubes intact with a gentle stir, and add the green onion tops just before serving. If the soup tastes too strong, add a small splash of hot water; adding more miso may make it saltier rather than better balanced.

Serving Suggestions

Serve the soup hot as a small first course or as part of a Japanese-style meal. It pairs naturally with a bowl of steamed rice, grilled fish, teriyaki chicken, or a simple vegetable dish. For a light lunch, add a modest portion of rice and a side of pickled vegetables. Because miso soup is usually served in smaller bowls than a main-course stew, the recipe makes four generous side portions; serve it in larger bowls if soup is the main part of the meal.

Set out the sliced green onion tops and sesame seeds separately if you are serving several people, so each person can choose how much garnish to add. A few drops of toasted sesame oil can make the bowl richer, but use a light hand: too much can cover the clean dashi and onion flavors. Serve soon after cooking for the best contrast between the warm broth, soft tofu, and fresh onion.

Variations

Make it vegetarian. Use kombu dashi or a vegetarian instant dashi instead of a bonito-based product, and check that the miso and any other packaged ingredients suit your needs. The soup will still be savory, although a kombu-only broth has a gentler, less fish-like aroma. Avoid assuming that all instant dashi is vegetarian, since many products include bonito.

Change the miso or vegetables. Red miso gives the soup a more robust, saltier flavor, so begin with 3 tablespoons (45 g), taste, and add more only if needed. Sliced mushrooms, such as shiitake, can simmer with the onion whites for a deeper flavor. Thinly sliced daikon also works; give it extra simmering time until tender before adding the tofu. These additions change the balance and make the soup heartier, so keep the miso amount adjustable.

Make a more substantial bowl. Add cooked udon noodles to individual bowls and ladle the finished soup over them, or serve the soup with rice on the side. If adding raw vegetables that need cooking, simmer them in the dashi before the tofu and wakame. Keep the miso out of the pan until those ingredients are tender, then finish the soup as directed. This preserves the miso’s aroma and prevents delicate ingredients from being overcooked.

Storage and Reheating

Cool leftovers promptly and refrigerate them within 2 hours in a covered container. The soup keeps for 3 to 4 days in the refrigerator, although the green onion tops lose their fresh color and the wakame becomes softer as it sits. If you expect leftovers, you can reserve some of the sliced green tops and add them fresh when serving. Keep the soup chilled rather than leaving it at room temperature while eating.

Reheat only the portion you plan to serve in a small saucepan over medium-low heat, stirring gently until it reaches 165°F (74°C), the USDA FSIS safe temperature for reheated leftovers. Avoid bringing it to a prolonged boil, which can affect the miso’s flavor and break up the tofu. A microwave also works: heat in a microwave-safe bowl in short intervals, stirring carefully between intervals, until the soup reaches 165°F (74°C). Freezing is possible, but tofu and wakame often become less pleasant in texture after thawing, so refrigeration is preferable for this recipe.

Frequently Asked Questions

Is Japanese green onion soup the same as miso soup?
This recipe is a type of miso soup: it uses a dashi base seasoned with miso and includes green onion, tofu, and wakame. Japanese miso soup has many household and regional variations, and it can be made with different vegetables, seaweeds, tofu, and styles of miso. Green onion is the focus here, rather than a fixed set of ingredients for every version.

Can I use regular scallions instead of Japanese negi?
Yes. Regular scallions, also sold as green onions, are a convenient substitute and are the ingredient used in the quantities above. They are thinner and usually more pungent than negi, so slice them finely and separate the white parts from the green tops. If using negi, its broad white stalk is especially good simmered in the broth.

What can I use if I do not have dashi granules?
Use 6 cups (1.42 L) prepared dashi, ideally kombu dashi for a vegetarian version or kombu-and-bonito dashi for a classic savory flavor. If you cannot find dashi ingredients or granules, a mild vegetable broth can work, but it gives the soup a different flavor and may be saltier. Choose a low-sodium broth and taste before adding soy sauce.

Should I boil miso soup?
Bring the dashi to a simmer to cook the onions and warm the tofu, but stir in the miso after turning off the heat. You can warm the finished soup gently if necessary; avoid a sustained boil. This keeps the broth smooth and helps retain the miso’s distinctive aroma.

Can I make the soup ahead?
You can prepare the dashi and slice the onions ahead, then refrigerate them separately in covered containers. For the best texture, cook the soup and add the miso close to serving time. If the complete soup is already made, refrigerate it within 2 hours and reheat the portion you need to 165°F (74°C); add fresh onion tops after reheating.

How do I keep the soup from tasting too salty?
Measure the dashi granules according to their package directions and start with the listed amount of miso. Dashi products and miso brands vary in saltiness, so taste before adding the optional soy sauce. If the soup is already too strong, dilute it with a little hot water or unsalted dashi rather than adding more tofu or miso.

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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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