Paper-thin white kombu from Tsuruga, Japan — hand-shaved from the core of Hokkaido ma-kombu. Wrap, cure, and plate. $61 per 100 sheets.
Battera Kombu — also known as Shiroita Kombu, or "white board kelp" — is the innermost core of premium Hokkaido ma-kombu, revealed only after craftsmen have shaved away every yielding outer layer. The outer shavings produce oboro kombu and tororo kombu; the intact inner core that remains is battera kombu.
The craft required to produce it without tearing the sheet is rare. Using a specialized blade called an Akita knife — a tool developed within Tsuruga's centuries-old kombu-processing tradition — craftsmen work inward through the kelp, releasing each layer cleanly. The final core must be separated whole, without a single perforation. This is why battera kombu is produced in limited quantities, even within Japan.
Tsuruga, on the Sea of Japan coast of Fukui Prefecture, is the historic gateway through which Hokkaido kelp traveled to the kitchens of Osaka and Kyoto. It remains one of the few places where this craft is still practiced at the highest level. The raw material — ma-kombu from the Donan coast of southern Hokkaido — is sourced from waters historically designated as tribute kelp for the Imperial Court, prized for its clean, high-umami dashi and dense cellular structure.
Ayako, Umami Curator at The House of Umami, has returned to Tsuruga more than once. On one visit, she was handed an Akita knife and invited to try the shaving process herself — pressing the blade against a block of ma-kombu, pulling sheets of oboro kombu away in long, careful strokes. The angle had to be exact. The pressure had to be sustained and even. A single misjudgment and the sheet tore.
What the craftsman showed her afterward was what has stayed with her since. When every layer of oboro kombu has been shaved away — one slow stroke at a time — a single thin core remains. One block of kombu. One sheet of battera kombu. The craftsman held it up between two fingers: barely wider than a thumb, semi-translucent, intact. What moved Ayako was not just the craft but its fragility. The craftsmen who still know this technique are dwindling — their average age already past sixty. The ma-kombu harvest has been thinning with each season's variation. And there is no certainty this skill will survive into the next generation. She had felt all of that in her own hands. The transience and scarcity of battera kombu — experienced firsthand — is why she carries it.
What the craftsman held between two fingers — and what arrives in each pack — measures approximately 4.8 cm × 14 cm (1.9 in × 5.5 in), cut to this specification with a tolerance of ±2 mm. As a handcrafted product, no thickness standard is defined; thickness varies naturally from sheet to sheet. The format is sized precisely for individual battera sushi portions and single-serve kombu-jime applications.
Conditioned with brewed vinegar during processing, the sheets are firm yet pliable at room temperature, semi-translucent when held to the light, and carry a rounded, deeply savory character with a mild acidity. That balance of umami and acidity is what makes battera kombu so effective as a wrapping material: it tempers richness, slows moisture loss, and transfers its savory depth gradually into whatever it contacts.
In Japan, it is traditionally laid over pressed mackerel sushi (battera) to protect the fish from drying, soften acidity, and create a continuous exchange of flavor as the sushi rests. Outside that tradition, battera kombu has found a home in some of the world's most technically ambitious kitchens — used as a curing wrapper for fish, shellfish, and poultry; deep-fried to a crackling crisp by Björn Franzén; and laid over a just-plated dish, where residual heat softens into an elegant, translucent finish.
