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1
Build the dashi. Place the kombu in 1.5 litres of cold water. Bring slowly to just below a simmer over medium heat. Remove the kombu just before the water boils. Add the katsuobushi, bring briefly to a bare simmer, then remove from the heat and allow the flakes to steep for 5 minutes. Strain through a fine sieve. The finished dashi should be pale amber, clear, and carry a clean marine fragrance without any bitterness.
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2
Pre-cook the daikon. Place the daikon rounds in a saucepan and cover with rice washing water — the cloudy starch water from the first rinse of raw rice. Bring to a simmer and cook for 15–20 minutes. Drain and rinse the daikon. This step cannot be skipped: the bitterness of unprocessed daikon, if not removed here, will permeate the entire broth. The rounds are ready when a skewer meets slight but not firm resistance at the centre.
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3
Season the dashi. Return the strained dashi to a wide, heavy pot. Add the light shoyu and mirin. Bring to a bare simmer and taste: the broth should carry quiet, layered umami — present but deliberately subtle. It is a permeation vehicle, not a soup to be drunk alone; it must be appropriately seasoned so that it will flavour every ingredient over long, slow cooking. Adjust shoyu if needed.
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4
Add the long-cooking ingredients. Lower the pre-cooked daikon rounds, konbu knots, konnyaku, ganmodoki, age-dofu, tsukune, and boiled eggs into the seasoned dashi. The pot must never boil — rapid boiling clouds the broth, breaks delicate items, and destroys the subtle flavour balance. Maintain the gentlest possible simmer: the surface should tremble, not roll. This is where the dish lives or dies. Daikon requires 2–3 hours of this unbroken low heat to become fully permeated, collapsing gently at the touch of a spoon; the broth must be working continuously throughout.
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5
After 45 minutes of simmering, add the chikuwa fish cake tubes. They require less time than daikon but must be given enough heat to absorb the broth through their hollow centres. They are ready when they have deepened in colour and feel pliant rather than springy.
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6
Replenish the broth as needed. As liquid reduces, add hot pre-seasoned dashi — never plain water — to maintain the level and the broth's integrity. The pot level should remain constant around the ingredients.
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7
In the final 10 minutes before service, lower the hanpen gently into the pot. It requires only 10 minutes of gentle heat; added earlier it will dissolve entirely. It is ready when it has swelled slightly and its surface has taken on a faint golden tinge from the broth.
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8
Rest and serve. For the fullest flavour, remove the pot from the heat, allow it to cool, and refrigerate overnight. The flavour integration that occurs over those hours is transformative — day-two oden is universally considered superior. Reheat the following day over the lowest possible flame, again never reaching a boil. Serve from the pot into deep bowls, ensuring each portion receives daikon, egg, ganmodoki, chikuwa, hanpen, and a measure of clear broth. Place a small mound of karashi beside each bowl.