Japanese Noodle Soup with Dashi Broth: Easy Kake Udon

This Japanese noodle soup is a simple kake udon: thick, chewy udon served in a clear broth flavored with dashi, soy sauce, and mirin. It comes together with a few pantry ingredients, and the gentle broth lets the noodles and fresh garnishes shine; seasonings and toppings vary by region and household.

Ingredients

8 cups (1.9 L) cold water
1 piece dried kombu, about 4 by 6 inches (28 g)
1 cup loosely packed katsuobushi, or dried bonito flakes (28 g)
1/3 cup Japanese soy sauce (80 ml)
1/4 cup mirin (60 ml)
1/2 teaspoon fine salt (3 g), plus more to taste if needed
14 oz dried udon noodles (400 g)
4 scallions, thinly sliced, about 1/2 cup (50 g)
4 oz kamaboko, Japanese fish cake, thinly sliced (115 g), optional
2 sheets toasted nori, cut into narrow strips (about 2 g), optional

Kombu and katsuobushi make a classic, savory dashi, the Japanese stock that gives this soup its layered flavor. Both are sold at Japanese and many Asian grocery stores. If katsuobushi is unavailable, use 1 tablespoon (6 g) instant dashi powder in the broth instead; check its label because some mixes already contain salt, and the flavor may be less delicate. For a vegetarian broth, replace the bonito flakes with 4 dried shiitake mushrooms (about 20 g), soaked in the measured water for at least 30 minutes, and simmer them gently with the kombu. The result is earthy rather than smoky. Mirin is sweet rice wine; if you cannot find it, use 3 tablespoons (45 ml) water plus 1 tablespoon (15 ml) sugar in its place. The broth will lose some of mirin’s rounded flavor.

Instructions

Prepare the ingredients, 12 minutes. Wipe the kombu with a damp cloth to remove any loose grit; do not scrub off its fine white powder, which contributes flavor. Slice the scallions and kamaboko, if using, and measure the soy sauce, mirin, and salt. Keep the noodles dry until the broth is ready, and set out four warm serving bowls.
Soak the kombu, 20 minutes. Put the kombu in a medium pot with the 8 cups (1.9 L) cold water. Let it soak for 20 minutes. This gives the water time to draw out flavor before heating. If you have extra time, a longer cold soak is fine, but it is not required for this recipe.
Make the dashi, 10 minutes. Set the pot over medium heat and warm it gradually for about 10 minutes, watching closely. Just before the water reaches a boil, remove the kombu; boiling it can make the stock slippery or bitter. Add the bonito flakes, turn off the heat, and leave them to steep undisturbed for 5 minutes. The flakes will sink as their flavor infuses the broth.
Strain and season, 3 minutes. Pour the dashi through a fine-mesh strainer into a clean pot or heatproof bowl. Avoid pressing hard on the flakes, which can cloud the broth or bring out a harsh taste. Return the clear stock to the pot, stir in the soy sauce, mirin, and salt, and warm it gently until steaming. Taste a spoonful: the broth should be savory, lightly sweet, and pleasantly seasoned, not as salty as a dipping sauce. Adjust with a small pinch of salt or a splash of water if needed.
Cook the udon, about 8 minutes. Bring a separate large pot of water to a boil. Add the dried udon and cook according to the package directions, using 8 minutes as a guide. Stir once or twice so strands do not stick together. Taste a strand near the end; it should be tender and springy, without a hard, chalky center. Drain the noodles and briefly rinse them under warm water to wash away excess surface starch. This keeps the finished broth clearer.
Assemble and serve, 1 minute. Divide the noodles among the four warm bowls. Ladle the hot broth over them, then add scallions and, if desired, kamaboko and nori. Serve promptly while the broth is hot and the noodles still have a pleasant chew.

Tips

Keep dashi below a rolling boil. Removing the kombu just before boiling and steeping the bonito off the heat are small steps that help the broth taste clean. If the water boils by accident, take it off the heat, remove the kombu, and continue with the flakes; the stock is still usable.
Use package timing for your noodles. Dried udon brands vary in thickness, so the package’s cooking time is more reliable than the 8-minute estimate. Start tasting a minute before the suggested finish, and drain as soon as the center is tender.
Season after making the stock. Soy sauce brands differ in saltiness, and instant dashi can be salty too. Start with the listed salt, taste the broth hot, and add more only if it needs it. A little water can soften an overly strong broth.
For a clearer bowl, keep the components separate. Rinsing drained udon removes loose starch. If you expect leftovers, store noodles and broth separately rather than leaving the noodles to soak up all the liquid.

Serving Suggestions

Serve each bowl as a light main meal, or offer smaller portions alongside rice, pickled vegetables, or a simple cucumber salad. The soup is satisfying on its own, but a small plate of tempura or edamame makes it more substantial. Put extra scallions, nori, and shichimi togarashi—a Japanese blend of chile and other spices—on the table so everyone can season their bowl. Add the spice gradually; its heat can build quickly.

Warm the bowls with hot tap water while you finish the broth, then empty and dry them before adding the noodles. This modest step helps keep the soup hot at the table. If serving several people, arrange the toppings before cooking the udon so the noodles can go straight from the pot into the bowls. Kake udon is best right after assembly, when the noodles are springy and the broth remains clear.

Variations

Vegetarian shiitake kombu udon: Make the broth with kombu and dried shiitake mushrooms instead of bonito. Soak the mushrooms in the measured water for at least 30 minutes, then remove the kombu before the water boils and simmer the mushrooms gently until the broth is fragrant. Strain and season as directed. Confirm that your soy sauce and any dashi powder are suitable for your dietary needs; some instant dashi contains fish.

Chicken udon: Add sliced cooked chicken as a topping, or cook boneless chicken separately and slice it before serving. If cooking raw chicken, check the thickest piece with a food thermometer and cook it to the USDA FSIS safe minimum internal temperature of 165°F (74°C). Keep raw chicken and its utensils away from the cooked noodles and garnishes.

Mushroom and vegetable udon: Simmer sliced shiitake, enoki, or button mushrooms in the seasoned broth until tender, then add spinach or bok choy near the end so the greens stay bright. A few tablespoons of sliced carrot also work; cut it thinly so it cooks quickly. These additions make the bowl fuller and add their own flavor, so taste the broth again before serving.

Cold-weather topping changes: Use a small spoonful of grated fresh ginger, toasted sesame seeds, or a little citrus zest in place of some of the usual garnish. These are accents, not ingredients to boil in the dashi: add them to individual bowls so their aroma stays distinct. For a richer bowl, add a few slices of aburaage, seasoned fried tofu, if available.

Storage and Reheating

For the best texture, refrigerate the broth and noodles in separate covered containers. Cool them promptly and refrigerate within 2 hours of cooking. The broth keeps for 3–4 days in the refrigerator; cooked udon is also best used within 3–4 days, though it softens as it sits. Store kamaboko and fresh garnishes separately according to their package directions, and do not leave assembled soup at room temperature for more than 2 hours.

Reheat the broth in a saucepan until steaming, then check that leftovers reach 165°F (74°C), the USDA FSIS reheating temperature. Add a splash of water if the broth tastes concentrated. Warm the noodles briefly in boiling water, or place them in the hot broth just long enough to heat through; prolonged simmering can make them soft. Assemble only the portions you plan to eat. You can freeze the broth for up to 2 months for best quality, but freezing cooked udon is not recommended because it tends to lose its chewy texture. Thaw frozen broth in the refrigerator before reheating.

Frequently Asked Questions

Is this the same as ramen? No. This recipe uses udon, which is thick and chewy, and a light dashi-based broth seasoned with soy and mirin. Ramen noodles and broths have many styles, often with a richer or more strongly flavored base. The two are different noodle soups, even though both are served hot with toppings.

Can I use frozen or fresh udon instead of dried? Yes. Frozen and fresh udon are convenient substitutes, but they cook much faster than dried noodles. Follow the package instructions and stop when the noodles are hot and tender; the recipe’s 8-minute estimate applies to dried udon. Drain them before dividing among the bowls so excess cooking water does not dilute the broth.

What can I use if I do not have kombu? The broth will still be useful without it, but it will have less of the gentle, savory depth that kombu contributes. Make the stock with bonito flakes alone, or use a measured amount of instant dashi according to its package. If using powder, taste before adding salt or soy, since the mix may already be seasoned.

Can I make the broth ahead? Yes. Make and season the dashi up to 3–4 days ahead, cool it promptly, and refrigerate it in a covered container. Reheat it gently before serving and cook the noodles fresh for the best texture. You can also freeze the broth for up to 2 months; thaw it in the refrigerator, then reheat it to 165°F (74°C) before serving.

Why is my broth cloudy? Common causes are boiling the kombu, pressing the bonito flakes while straining, or adding noodles without rinsing off loose starch. Cloudiness does not necessarily mean the soup is spoiled, but it can make the broth taste less clean. Keep the stock at a gentle heat, strain without squeezing, and rinse the drained noodles briefly before assembling.

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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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