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1
Score each chestnut at its base with a sharp knife, cutting through the outer shell without piercing the flesh. Place in water at 80 °C — not boiling — and hold for 5 minutes. Boiling will create fragile, crumbling flesh. Working one chestnut at a time and keeping the remainder submerged and warm, peel away the outer shell and then the inner shibukawa with a paring knife; cold shells re-adhere to the flesh and cannot be cleanly removed. Reserve chestnuts as required for each preparation.
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2
Kuri kinton — sweet potato base: place the peeled sweet potato rounds in a pot with 500 ml water and the cracked kuchinashi pods. Simmer until the sweet potato is completely tender. This is where the dish lives or dies: the kuchinashi pods must be present throughout this stage — without their chemical contribution the preparation oxidises to an unappetising grey-yellow rather than the required gold. Remove the pods. Drain and pass the sweet potato through a fine sieve (uragoshi) for an exceptionally smooth texture.
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3
Kuri kinton — assembly: combine the sieved sweet potato with the sugar in a clean pot over low heat, stirring until the sugar dissolves and the paste tightens. Fold in the reserved simmered whole or broken chestnuts. The paste should be sweet, but the chestnut's natural earthiness must remain detectable — over-sweetening until the preparation is cloying is the principal fault. The finished kinton holds its shape when a spoonful is lifted and dropped: dense, golden, coherent.
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4
Shibukawani — syrup: dissolve the sugar in 600 ml water over medium heat to form a clear syrup. Add the chestnuts with their inner shibukawa skins fully intact — do not remove the skins; they are the preparation's identifying feature and their tannin bitterness is essential to balance the syrup's sweetness. Simmer gently until the chestnuts are tender throughout and the syrup has deepened in color. The syrup should taste sweet with a distinct bitter-tannin undertow from the skins.
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5
Kuri gohan — rice: soak the fully peeled whole chestnuts in cold water for 30 minutes — this prevents the flesh from cracking during cooking. Drain. Place the rinsed rice, chestnuts, salt, and measured water together in the rice cooker. The chestnuts and rice cook simultaneously, the chestnuts absorbing the cooking liquid. Do not substitute jarred chestnuts: their altered water content renders them mushy. The finished rice should carry whole, intact chestnut pieces with a nutty richness absorbed into each grain.