Udon Noodle Soup (Kake Udon)

Method

1. 1Make 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 (boiled kombu gives the dashi a heavy kelp smell). 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. 2Season the broth. Pour the dashi into a clean saucepan. Add the soy sauce, mirin, sake, and salt. For the pale Kansai broth this recipe describes, use usukuchi (light-coloured Japanese soy sauce); with regular dark soy sauce (koikuchi) the same 2 tablespoons give a darker, amber Kanto-style broth, which is just as correct. 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. 3Cook the noodles separately. If you are topping the bowls with egg, soft-boil it first: 6.5 minutes in boiling water, then straight into cold water, peel and halve. Cook the udon in a separate pot of boiling unsalted water — not in the broth, because the noodles release starch that clouds it. Dried and uncooked fresh udon must always be boiled this way; pre-cooked udon (vacuum-packed or frozen) can also be warmed straight in the broth if you do not mind it slightly cloudy. 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, about 250 g of noodles in each.
4. 4Assemble and serve immediately. Ladle the very hot broth over the noodles — enough to mostly submerge them. Scatter the sliced scallions 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. 5Variations. 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.