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1
Day one (28–30 December). Place dried black soybeans in a large bowl with the iron nail or iron foil and cold water to cover by 10 cm. Soak overnight. The iron begins its work on the anthocyanins immediately. The soaking water will turn dark; this is correct.
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2
Place salt-packed kazunoko in a separate bowl of cold water. Soak for 24 hours, changing the water two or three times. At the end of soaking, peel the delicate outer membrane from each lobe with a fingernail, working gently and patiently. This is the step on which the dish lives or dies: rough handling tears the membrane and destroys the integrity of the egg rows, producing broken roe that cannot be restored. Each lobe should emerge whole, glistening, and fully intact, its rows of tiny eggs visibly separate.
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3
Drain the soaked kuromame, reserving the soaking liquid. Transfer beans and iron nail to a heavy pot with the soaking liquid, sugar, soy sauce, and mirin. Bring to a gentle simmer. Skim any foam. Maintain a bare simmer, covered, until beans are completely tender — several hours. The cooking liquid should reduce to a glossy, deeply sweet syrup. The beans must be substantially sweet: timid seasoning produces flat, unpalatable beans. The finished bean should be jet black, tender throughout, and carry a flavour that registers clearly as a sweetened preparation, not merely as cooked legume. Remove the iron nail before serving.
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4
Make the tazukuri. Heat a dry pan over medium heat and add the dried sardines. Fry, stirring constantly, until the sardines are crisp and fragrant — they will colour slightly. In a small saucepan combine sugar, soy sauce, mirin, and sake; reduce to a thickened syrup. Add the crisped sardines and toss briefly to coat. Spread immediately on parchment paper in a single layer to set. When cooled, the sardines should be individually separable, not clumped. Test by lifting one: it should hold its form.
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5
Make the namasu. Julienne daikon and carrot at a 4:1 ratio. Salt lightly, toss, and press under a weight for 20 minutes. Squeeze out excess moisture firmly. Combine rice vinegar, sugar, and salt to make sanbaizu; stir until sugar dissolves. Dress the daikon and carrot and allow to rest until the flavour is fully integrated. The finished namasu should be bright — white daikon, vivid orange-red carrot — crisp, and cleanly acidulated.
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6
Make the datemaki. Blend grilled or steamed hanpen with eggs, mirin, and sugar until smooth. Cook the mixture in a lightly oiled tamagoyaki pan over low heat, covered, until just set. While still hot, roll tightly in a bamboo mat and secure with bands; allow to cool in the mat. The fish protein sets the roll cleanly. Unwrap when cool to reveal a scroll-shaped omelette with a defined spiral cross-section.
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7
Make the nimono. Combine dashi, soy sauce, and a generous measure of mirin in a wide pan. Bring to a simmer. Add root vegetables in order of density: gobo first, then lotus root, then taro. Simmer until each vegetable is tender but retains a clear, defined shape — test with a skewer, which should enter without resistance but not cause the piece to collapse. Mushy vegetables signal insufficient attention to cooking time. Remove each variety as it reaches this point.
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8
Dress the kazunoko lobes with the combined dashi, light soy sauce, and mirin. Allow to rest briefly so the dressing penetrates without overwhelming the delicate roe. Each row of tiny eggs should remain intact and glistening before boxing.
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9
Assemble the jūbako. Arrange the ichidanme (first tier) with kazunoko, kuromame, and tazukuri. The second tier receives namasu, datemaki, and sliced kamaboko in alternating red-and-white sequence. The third tier holds the nimono root vegetables. The visual composition of each tier is as deliberate as a painting: contrasting colours, textures, and heights are placed with intention. No ingredient overlaps unless intentionally. The completed box should be self-evidently a considered composition.