Whatever dashi you have can make a good udon broth. Build it from scratch just for the udon, though, and you will taste the difference.
I want to show you how to make the delicate soup Japanese udon shops serve, from the dashi up.
Kake udon
Recipe Snapshot
- What is it? Kake udon is a bowl of udon in hot broth with barely any toppings. It forms the base for kitsune, tsukimi, and most other udon dishes named after their toppings.
- Flavor profile: Freshly-steeped bonito flakes give a delicate, appetizing aroma. Slurp, and the anchovies and kombu come through underneath, with gentle hon mirin sweetness. No harsh saltiness, light enough to drink up.
- Why this recipe works: Removing the kombu and dried anchovies before boiling, then steeping the bonito flakes for just seconds, keeps off flavors out and the dashi clear. These careful steps recreate udon-shop broth.
- How to make it: Soak and heat anchovies and kombu, steep bonito flakes briefly in boiled dashi, and strain. Cook off mirin in the same pot, add dashi and soy sauce, then boil noodles.
- What to expect: Allow about 60 minutes, 35 for hands-off preparation and 25 for cooking. Deciding when to remove kombu and anchovies takes judgment. Taste once tiny bubbles appear at the pot’s edge.
What Is Kake Udon?
To make kake udon, boil udon noodles and pour plenty of hot broth over them. Its name comes from kakeru, “to pour over.” This simple Japanese noodle dish is the base for many warm udon variations.
Fried tofu simmered sweet in sugar and soy sauce makes kitsune udon, and an egg makes tsukimi udon. In Kanto, the region around Tokyo, tenkasu (tempura bits) makes it tanuki. Green onion or a slice of kamaboko, a fish cake, still counts as kake. Kanto uses koikuchi, standard soy sauce, for a dark broth. Kansai (Kyoto and Osaka) serves pale su udon. Sanuki (Kagawa’s old name) is golden from anchovy dashi.
In Kanto, bonito dashi seasoned with koikuchi soy sauce produces a dark broth. Many shops simply use the same tsuyu they serve with soba. Kansai’s pale su udon has a dashi made mainly from kombu and seasoned with usukuchi, a light-colored soy sauce. Sanuki’s golden broth comes from dried anchovies. These fish have long been a local ingredient in Kagawa, where the island of Ibukijima is famous for them. Golden anchovy broth surrounding translucent noodles is the classic appearance of Sanuki udon.
A folding screen depicting the Konpira festival around 1700, near the end of the Genroku era, shows 3 udon shops in front of the gate. Soy sauce was a luxury at the time, and we do not know exactly what a bowl of Sanuki udon looked like then. Records from the late Edo period, in the early 1800s, describe hot noodles served with dipping sauce in a small vessel. The large bowls filled with broth that we know today appeared later.
I do not stop at the usual awase dashi blend of bonito flakes and kombu. I add dried anchovies, because this one is built for udon. Sanuki shops also add mackerel flakes, and round herring flakes, to their pots. I keep mine to dried anchovies, kombu, and bonito flakes. To season it, I use equal amounts of koikuchi soy sauce and hon mirin, with no sugar or extra salt. This makes my version a little different from each of the Kanto, Kansai, and Sanuki styles. I want the sweetness of mirin and the savory richness of the dashi to carry the broth without letting it become too salty. The better the dashi tastes, the less salt it needs.
Udon Noodle Soup Ingredients
- Iriko (dried anchovies): These small dried fish give my broth its body. They are called iriko in western Japan and niboshi in eastern Japan. Outside Japan, look for bags labeled “dried anchovies/sardines” at Asian supermarkets. Korean dried anchovies intended for stock work equally well. Size does not matter, but appearance does, so choose shiny, silver fish with intact bellies.
- Kombu: You can use any variety, though lately I use ma-kombu most of the time. It produces clear, golden dashi with a clean sweetness. Korean kelp labeled dasima is the same seaweed and can be used in exactly the same way.
- Bonito flakes (katsuobushi): Choose thin, fluffy shavings, called hanakatsuo, because this recipe extracts their aroma in just a few seconds. These are the ordinary bonito flakes sold in bags. Flakes with the dark bloodline removed help keep the broth clear.
- Udon noodles: Their mild wheat flavor lets the broth shine. If you are taking the time to make dashi from scratch, it is worth choosing the noodles with equal care. I prefer my homemade udon recipe, followed by fresh udon, then good frozen udon. Thick, chewy Sanuki-style noodles work particularly well with this broth, and dried udon is also an option.
Substitution Ideas
- Iriko → Kombu and katsuobushi only: Without dried anchovies, the kombu and bonito flakes still make a standard awase dashi, an everyday blended stock. It will lack the rounded, full body that the anchovies provide.
- Standard Japanese soy sauce → Usukuchi (light-colored Japanese soy sauce): This gives you a paler broth, similar to Kansai-style udon, but also makes it slightly saltier. Start with less than the recipe’s amount and taste as you add it.
- Standard Japanese soy sauce → Chinese light soy sauce: The flavor is different from Japanese soy sauce, and that difference is noticeable in such a clear broth.
Substitutions that I don’t recommend:
- Niboshi powder instead of iriko: The heads and guts are ground into the powder along with the fish, making the broth cloudy and bitter.
- Chinese dark soy sauce instead of standard Japanese soy sauce: Its thickness and sweetness are too much for this broth. Choose Chinese light soy sauce if you want to use a Chinese variety.
- Vinegar and sugar instead of mirin: The vinegar’s acidity upsets the balance of the broth.
Hunting for another Japanese pantry swap? My guide to Japanese ingredient substitutes is the place to look.
How to Make My Udon Soup
Before you start (Mise en place):
- Remove the heads from the dried anchovies. Use both thumbs to press along each fish’s back and split it open, then remove the black guts.
- Cut the green onions into thin rounds.
To develop this recipe, I used a 20cm stainless steel saucepan.
i. Put the kombu and dried anchovies in a pot of water. Cover and soak for at least 30 minutes.
ii. Move the pot to the stove top and heat over medium-low. Adjust the heat so that it takes about 10 minutes for tiny bubbles to appear around the edge of the pot.
iii. Taste as soon as you see those bubbles. If the broth has a distinct flavor, remove both the kombu and the fish. If it still tastes watery, keep it over low heat a little longer.
Never let it boil. Boil it, or keep it hot too long, and the kombu releases slime and murky flavors. If the broth needs extra time over low heat, keep tasting and pull the kombu and fish out the moment the flavor is there. Take them out together, since the next step brings the dashi to a full boil.
You can reduce the amounts if the ingredients feel too expensive. The dashi will have a gentler aroma and flavor, but it will still taste good. Heating the kombu longer to compensate only draws slime and harsh flavors out of it. If you have the time, you can soak the kombu and fish overnight in the fridge. I think it’s the safer and better way.
i. Remove the kombu and sardines and save them for later if you want to make a second batch of dashi. Increase the heat and bring the dashi to a full boil.
ii. Add about a ladleful of cold water to lower the temperature to 90-95°C/194-203°F. Immediately add the bonito flakes.
iii. After about 10 seconds, small bubbles will begin to rise again. Turn off the heat and use a ladle to skim away any foam on the surface.
Yes. In water at around 90°C/194°F, thin bonito flakes release their aroma and umami in a few seconds to a minute. Turning off the heat after about 10 seconds is enough. Simmering longer will not extract more umami. It drives away the aroma and brings out astringent, bitter flavors.
i. Line a strainer with a cheese cloth/paper towel and place it over a large heatproof bowl. Pour the dashi through it.
ii. Allow the liquid to drip through until it stops. Do not press or squeeze the ingredients. Pressing forces harsh flavors into the clear broth. Your dashi is now ready. Store any you will not use right away according to the recipe card notes.
You can use the strained dried anchovies, kombu, and bonito flakes again to make a second dashi.
i. Quickly rinse the pot you used to make the dashi, then add the mirin. Let it bubble over medium heat for 30 seconds to 1 minute to cook off the alcohol.
ii. Pour in the dashi. When the mixture is lukewarm, add the soy sauce and continue heating, keeping it below a boil.
iii. Once the broth is hot enough to serve, spoon out a little and let it cool briefly before tasting. Add more soy sauce in small amounts if needed.
Heat makes broth taste less salty than it actually is. Taste every time, since evaporation changes from burner to burner and day to day.
iv. Keep the finished broth warm over low heat.
If soy sauce boils with the mirin, its fresh, straight-from-the-bottle aroma turns into the sweet smell of a cooked-down sauce. Letting the mirin bubble alone first cooks off its alcohol. Add the soy sauce last, then keep the broth below a boil to preserve that fresh aroma.
In any dish built on dashi, everything starts with the dashi. The first extraction is called ichiban dashi. Made this strong, it tastes good enough to drink without any added salt. Its strength determines how much salt you need, supplied here by soy sauce. The richer your dashi, the less soy sauce it takes, so always taste before adding more. That process of tasting and adjusting is part of the pleasure of Japanese cooking.
i. Bring a large pot of water to a boil and cook the udon according to the package instructions. Keep it at a rolling boil throughout.
ii. If using dried or fresh udon, rub the cooked noodles thoroughly under running water, then rest in cold water, to firm them up. Drain in a strainer.
iii. If using frozen udon, follow the package cooking instructions and use the noodles without rinsing.
i. Just before serving, put the rinsed noodles in boiling water for 15 to 30 seconds to heat them through again.
ii. Reheat the broth and divide it among the bowls. Gently separate the noodles with chopsticks and slide them into the broth.
iii. Add the green onions and any other toppings you like, then serve immediately.
Finishing the broth before cooking the noodles helps preserve both the noodles’ chew and the dashi’s aroma until you sit down to eat.
If you follow the default recipe, it will yield 5 servings.
Tips for the Best Kake Udon
- Choose soft water if your tap water is hard. Hard water can leave kombu dashi cloudy and tasting of minerals, even though it extracts about the same amount of umami as soft water.
- Wait for the noodles to float before stirring. Moving udon around with chopsticks while it is still on the bottom can break it. Once the noodles float, gently separate them in the water, one strand at a time.
- Warm the bowls first. Hot kake udon belongs in a hot bowl. A cold one can turn the whole serving lukewarm in an instant. Fill the bowls with hot water and empty them just before adding the noodles and broth.
Get those 3 right, and the bowl reaches the table with clear dashi and whole noodles, still steaming.
Storage & Meal Prep
Fridge: Cooled and covered, dashi or broth keeps 2-3 days.
Freezer: Freeze only unseasoned dashi, up to 2 weeks. Freezing dulls soy sauce and mirin aroma, so season after thawing. Uncooked homemade noodles keep 1 month.
Meal prep: Soak anchovies and kombu in the fridge overnight. Add bonito flakes on the day. Udon should always be cooked fresh.
Reheating: Warm to serving temperature without boiling.
What to Serve With Udon Noodle Soup
- Crispy Vegetable Kakiage
- Inari Sushi
- Chikuwa Isobe Age (Fish Cake Tempura)
- Shrimp Tempura (Ebiten)
Kake Udon Troubleshooting
The ingredients may not have soaked long enough, or the water may have heated so quickly that bubbles appeared at the edge before enough umami was extracted. If the kombu and dried anchovies are still in the pot, keep them over low heat a little longer and taste before removing them. If you have already taken them out, leave the soy sauce bottle alone and finish the broth as it is. Extra soy sauce adds salt without fixing the weak dashi, so the broth ends up thin and salty at once. Soak the next batch overnight.
This can happen if the kombu or dried anchovies boiled, if some guts remained in the fish, or if you pressed the bonito flakes while straining. Straining again will remove fine particles, though it cannot clear fat that has already mixed into the broth. Gently pour it through a strainer lined with a paper towel, without squeezing, and use the broth as it is. For the next batch, remove the kombu and fish before boiling and let the dashi drain through the strainer without pressing.
The kombu may have boiled or been cut into pieces before going into the pot. Boiling makes it release slime. Remove the kombu as soon as you notice and stop heating. Continuing to boil will not clear it. Next time, leave the kombu whole and remove it when tiny bubbles appear around the edge of the pot.
More Japanese Noodle Recipes
- Kake Soba Hot Buckwheat Noodle Soup
- Niku Udon Beef Noodle Soup
- Japanese Curry Udon
- Tori Nanban Udon with Chicken and Leek
For soba in a hot bowl, or udon topped with beef, curry, or chicken and leek, see my Japanese Noodle Recipes.
Did You Try This Recipe?
I would love to hear your thoughts!
💬 Leave a review and ⭐️ rating in the comments below. 📷 I also love to see your photos – submit them here!
Simple Udon Noodle Soup (Kake Udon)
Ingredients
Dashi
- 30 g dried sardines (niboshi) sold as dried anchovies or iriko
- 1000 ml water preferably soft water
- 10 g dried kelp (kombu)
- 15 g bonito flakes (katsuobushi) thin shavings
Broth
- 3½ tbsp mirin
- 3½ tbsp Japanese soy sauce (koikuchi shoyu)
Noodles and Toppings
- 5 tbsp finely chopped green onions
- 5 portions udon noodles
The ingredient brands and tools I trust are in my Japanese pantry guide and my cooking tools guide.
Can’t find certain Japanese ingredients? See my substitution guide here.
Instructions
Make the Dashi
- Pull the heads off 30 g dried sardines (niboshi). Split each fish along its back and remove the black guts.
- Pour 1000 ml water into a pot, add 10 g dried kelp (kombu) and the fish, cover, and soak for 30 minutes.
- After 30 minutes, set the pot over medium-low heat. Keep the flame low enough that tiny bubbles appear around the rim in about 10 minutes. Keep it below a boil.When tiny bubbles cling to the rim, taste the dashi. If the flavor is clear and full, lift out the kombu and fish together. If it tastes weak and watery, give it a little longer over low heat, then lift them out.
- Raise the heat to a rolling boil. Pour in about a ladleful of cold water (about 70 ml) to cool the dashi to 90 °C (194 °F)–95 °C (203 °F), and add 15 g bonito flakes (katsuobushi) at once. When small bubbles rise again, about 10 seconds later, turn off the heat. Skim off any foam with the ladle.
- Pour the dashi into a strainer lined with a cheese cloth or kitchen paper, and wait for the clear dashi to drip through slowly on its own. Do not press or squeeze the flakes.
Season the Broth
- Rinse out the pot and pour in 3½ tbsp mirin. Bubble it over medium heat until the alcohol cooks off, 30 seconds to 1 minute.
- Pour in the strained dashi. When it is lukewarm, stir in 3½ tbsp Japanese soy sauce (koikuchi shoyu) and heat the broth until it is hot enough to eat, keeping it off the boil. Cool a spoonful briefly and taste. If it needs more, add soy sauce in small splashes, then hold the broth warm over low heat.
Cook the Udon and Serve
- Bring water at least 10 times the weight of the noodles to a boil. Cook 5 portions udon noodles following the package directions, keeping the water at a full boil. Do not add cold water. Fill your serving bowls with hot water to warm them.
- Reheat the broth and ladle it into the bowls. Tease the noodles apart with chopsticks and lower them in. Scatter the green onion over the noodles, add toppings of your choice, and serve right away. Enjoy!
Followed your recipe (vegan/vegetarian dashi) for a school assignment (nutrition class), and was very happy with the outcome of the dish. My brother enjoyed trying it as well. I will come back to this simple and easy-to-follow recipe if the occasion to make kake udon arises again for me. Thank you.
Hi Jamin,
Thank you for trying my recipe, I’m happy to hear you and your brother enjoyed it.
I hope your assignment went well! All the best.
Perfect noodles and dashi broth! Brings back wonderful memories from Japan.
Domo arigato gozaimasu, sensei!
Hi Andral,
Thank you so much for your comment! I’m happy that this recipe brought back good memories of Japan for you! 🙂
Yuto
wonderful recipe, will try 🙂
Thank you, Adreena! I hope you will enjoy making it! 🙂