JapanThe single most important thing you can do for udon soup is make proper dashi. The broth is almost entirely dashi — the soy sauce, mirin and salt are just seasoning added to dashi, not a substitute for it. Dashi powder is convenient but produces a flat, slightly artificial tasting broth. Dashi packets (teabag-style packs containing bonito, kombu, and sometimes shiitake) take 5 minutes and produce a noticeably better result. Homemade dashi from kombu and katsuobushi takes 30 minutes and produces a genuinely beautiful broth. If you are making udon soup for the first time and wondering why restaurant udon tastes different, the answer is almost always the dashi.
The Kansai-Kanto regional difference comes down to soy sauce quantity and type. Kansai (Osaka, Kyoto) uses less soy sauce, and specifically usukuchi (light-coloured soy sauce) — so the broth is pale gold, almost colourless, with a clean, elegant flavour. Kanto (Tokyo) uses more dark soy sauce — the broth is darker and more assertive. Neither is more authentic: they are regional styles. Use whichever you prefer. Light soy sauce (usukuchi) is slightly saltier than dark despite its paler colour — adjust the quantity accordingly.
Udon Noodle Soup (Kake Udon)
By Sergei Martynov
Thick, chewy wheat noodles in a clear, golden dashi broth seasoned with soy sauce and mirin. Kake udon (かけうどん) is the most fundamental form of udon soup — the noodles, the broth, and a scattering of spring onion. Nothing else. It is the dish that demonstrates why dashi is called the soul of Japanese cooking: the broth is nearly colourless yet layered with umami, lightly sweet from the mirin, and clean in a way that Western stocks rarely achieve. Udon is a specialty of the Kagawa region (Sanuki udon) but is eaten everywhere in Japan. The Kansai version uses a lighter, more delicate broth; the Kanto version uses a darker, more assertive soy. This recipe follows the Kansai style. Make the broth right and the noodles will take care of themselves.
What you'll need
Ingredients
- 300 g
See recipes with fresh or frozen udon noodlesfresh or frozen udon noodles (Sanuki-style thick, chewy noodles are best — cook separately in boiling water)
i - 700 ml
See recipes with dashi stock — homemade from kombu + katsuobushidashi stock — homemade from kombu + katsuobushi, or from dashi packets, or 1 tsp dashi powder dissolved in 700 ml hot water
i - 2 tbsp
See recipes with soy saucesoy sauce (light soy / usukuchi for Kansai-style pale broth, or regular for Kanto-style darker broth)
i - 2 tbsp
- 1 tsp
See recipes with sake or dry sherrysake or dry sherry (optional but adds depth)
i - 0.5 tspSee recipes with fine salt — adjust to taste
fine salt — adjust to taste, soy sauce brand varies in saltiness
i - 2
See recipes with spring onionsspring onions, finely sliced — for serving
i - 1 tsp
See recipes with shichimi togarashi or ichimi togarashi — for the tableshichimi togarashi (Japanese 7-spice chilli blend) or ichimi togarashi — for the table
i - 2 slices
See recipes with kamaboko or soft-boiled eggkamaboko (fish cake) or soft-boiled egg, halved — optional toppings
i - 1 sheet
See recipes with norinori (toasted seaweed), cut into rectangles — optional topping
i
How to make it
Instructions
- 1
Make the dashi. The broth is everything in udon soup — the noodles and toppings are secondary. For homemade dashi: place a 10 cm piece of kombu in 800 ml cold water and soak for 20 to 30 minutes. Place over medium-low heat and slowly bring toward a simmer. Remove the kombu just before it reaches a full boil (boiling makes dashi bitter). Add 10 to 15 g of katsuobushi (bonito flakes), turn off the heat, and let steep for 5 minutes. Strain through a fine-mesh sieve without pressing. The result should be a pale amber, clear, subtly oceanic stock. For dashi powder: dissolve 1 teaspoon in 700 ml of hot water. For dashi packets: follow the packet instructions. Homemade gives the cleanest, most complex result; dashi powder is the quickest shortcut.
- 2
Season the broth. Pour the dashi into a clean saucepan. Add the soy sauce, mirin, sake, and salt. Bring to a gentle simmer over medium heat — not a rolling boil. Taste: the broth should be savoury, lightly sweet, and clean. If it tastes flat, add a pinch more salt; if too salty, add a splash of water. The colour should be a clear pale gold for Kansai-style or a deeper amber for the Kanto version. Keep warm over the lowest heat while the noodles cook. The broth must be very hot when served — udon soup goes cold quickly.
- 3
Cook the noodles separately. Always cook udon noodles in a separate pot of boiling unsalted water — not in the broth. Noodles release starch that will cloud and thicken the broth. For frozen udon: add to boiling water for 1 to 2 minutes until just loosened and heated through. For fresh vacuum-packed: 2 to 3 minutes. For dried: follow the package, but cook 1 minute less than stated. Drain well. Rinse briefly with hot water to remove surface starch. Divide between two deep bowls.
- 4
Assemble and serve immediately. Ladle the very hot broth over the noodles — enough to mostly submerge them. Scatter spring onions over the top. Add any additional toppings: kamaboko fish cake, soft-boiled egg, nori, or tempura (if making Tempura Udon). Serve shichimi togarashi on the side for each person to add to their own taste. Udon soup must be served and eaten immediately — the noodles continue absorbing broth and soften as they sit. This is not a dish that waits.
- 5
Variations. Kitsune udon: place an aburaage (fried tofu pouch, simmered briefly in soy, mirin, and dashi) on top of the noodles before pouring the broth. Tempura udon: add a piece of shrimp or vegetable tempura on top. Niku udon (meat udon): cook thin slices of beef or pork in the broth for 1 to 2 minutes before ladling over the noodles. Curry udon: add 1 tablespoon of Japanese curry paste (from a roux block) to the broth and whisk until dissolved.
Frequently Asked Questions
What is dashi and how do you make it?
Dashi is Japan's foundational soup stock, made primarily from two ingredients: kombu (dried kelp, which provides glutamic acid umami) and katsuobushi (dried bonito flakes, which provide inosinic acid umami). The combination is synergistic — together they produce an umami more powerful than either provides alone. To make: soak kombu in cold water 20 to 30 minutes, heat gently to just below boiling, remove kombu, add katsuobushi, steep 5 minutes, strain. Vegan dashi: use kombu only, or kombu plus dried shiitake mushrooms. The result is a very different flavour profile but still excellent. Instant dashi powder is available widely as a quick substitute.
What kind of udon noodles should you use?
Frozen Sanuki-style udon noodles (from Kagawa prefecture, the 'kingdom of udon') are widely considered the gold standard for home cooking — they cook in 1 to 2 minutes and have the characteristic thick, round, extremely chewy texture. Vacuum-packed fresh udon are a good second choice. Dried udon noodles work but produce a significantly softer, less chewy result — the texture gap between dried and frozen is considerable. If only dried are available, cook them 1 minute less than the package instructs.
What toppings are traditional for udon soup?
The most traditional is simply sliced spring onion (negi), which appears in virtually every bowl. Kamaboko (fish cake, the pink-and-white semicircle) is classic. Beyond these, toppings define the named varieties: aburaage (fried tofu pouch) = Kitsune Udon; tempura = Tempura Udon; thin beef = Niku Udon; wheat gluten (fu) and vegetables = Nabeyaki Udon. Plain kake udon with only spring onion is the simplest and arguably the purest form.
Can you make udon soup vegetarian or vegan?
Yes, easily. Replace the standard dashi (made with bonito) with kombu-only dashi (soak kombu in cold water for 30 minutes, heat to just below boiling, remove) or kombu-shiitake dashi (add dried shiitake to the kombu water during soaking). The resulting broth has a different flavour — earthier, slightly more intense — but is very good. Use tamari instead of soy sauce if also gluten-free. Tofu, aburaage, wakame seaweed, mushrooms, and spinach are all excellent vegan toppings.
Can you cook the udon noodles directly in the broth?
No. Udon noodles release a significant amount of starch as they cook, which clouds and thickens the broth. A properly made udon broth is clear — you should be able to see the noodles through it. Always cook the noodles separately in plain boiling water, drain them, then pour the hot broth over them in the serving bowl. If you want very thick, almost gravy-like soup, this is a different dish called ankake udon, where the broth is intentionally thickened with cornflour.
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