Japanese Yakiimo and Yaki-mochi: Fire-Roasted Simplicity and Street Vendor Culture

Ingredients

• For the yakiimo
• 4 beni haruka satsumaimo (Japanese sweet potato), scrubbed clean, skin intact; naruto kintoki or gorosima as regional alternatives
• as needed newspaper, dampened with water
• as needed aluminium foil, to wrap each dampened-newspaper parcel
• For the yaki-mochi
• 4 plain mochi cakes (kiri-mochi), cut or pre-cut blocks, at room temperature
• For the yaki-mochi — kinako-kuromitsu accompaniment
• 4 tbsp kinako (roasted soybean flour)
• 4 tbsp kuromitsu (black sugar syrup)
• For the yaki-mochi — nori-soy accompaniment
• 4 sheets nori, full toasted sheets, halved
• 4 tsp soy sauce

Method

1. 1
   Heat the oven to 120°C. Dampen a sheet of newspaper under running water until evenly moist but not sodden. Wrap each satsumaimo in the damp newspaper, then enclose tightly in aluminium foil. The newspaper layer replicates the moisture-retention and even radiant heat of the traditional river-stone bed.
2. 2
   Place the wrapped satsumaimo directly on the oven rack. Roast for a minimum of 60 minutes without disturbing them. This is where the dish lives or dies: the 80–85°C internal temperature window must be sustained long enough for the beta-amylase enzymes to convert potato starch to maltose. High heat destroys this enzyme window and with it the deep, honeyed sweetness that defines yakiimo; the window cannot be recovered once lost. The potato is ready when it yields completely to firm pressure through the foil — dense resistance means the conversion is incomplete.
3. 3
   Remove from the oven and allow to rest, still wrapped, for 5 minutes. Steam redistributes through the interior, softening the flesh further. Unwrap at the table. Split the skin lengthwise with a single cut — do not cut before service. The reveal of the caramelized, almost syrupy, amber interior is integral to the dish.
4. 4
   For the yaki-mochi: set a wire mesh over a gas flame or charcoal at medium heat. Place the mochi blocks directly on the mesh. Do not move them. As heat builds, the surface will begin to blister and swell visibly; after several minutes the edges will show the first signs of char. The mochi is ready when the exterior is fully puffed and lightly charred at the edges and the block holds its shape but shifts with the weight of a spatula — the interior has softened to a stretchy, sticky center.
5. 5
   Serve yaki-mochi immediately with the chosen accompaniment. For kinako-kuromitsu: dust the hot mochi generously with kinako, then drizzle with kuromitsu. For nori-soy: brush the hot mochi with soy sauce, then wrap immediately in a half-sheet of nori — the heat of the mochi causes the nori to adhere and soften against it. Both versions are ready when the accompaniment is fully incorporated and the mochi surface is no longer releasing steam.