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1
Prepare a large bowl of ice water deep enough to submerge the bonito block. Have it ready beside the heat source before searing begins. Set out all accompaniments — grated garlic, grated ginger, sliced myoga, shiso, and spring onion — on a serving plate; they must be at the table before the fish is cut.
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2
Ignite the wara (rice straw) in a fireproof vessel or, for home cooking, bring a blowtorch to full intensity held 1 cm from the surface. Skewer the bonito block lengthwise to hold it securely. Hold the skin side directly over the burning wara or blowtorch flame. Sear for 10–15 seconds maximum at the highest possible heat — the skin must blister, char at the edges, and release a visible plume of smoke. Turn and sear the flesh sides for no more than a few seconds each. This is where the dish lives or dies: interior cooking begins the moment the sear exceeds 15 seconds, destroying the raw character that defines tataki.
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3
Transfer the seared block immediately to the ice bath. Hold it submerged for 30–60 seconds until the exterior surface is cool and firm to the touch. Remove and pat dry with clean cloth.
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4
Cut the block into slices 1–1.5 cm thick, using a single drawing stroke of a sharp knife. The cross-section must show a thin band of caramelized, opaque, smoke-marked exterior giving way immediately to raw, translucent, deep-red flesh within. Thin slicing eliminates this contrast and defeats the preparation.
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5
Arrange the slices overlapping on a plate. Lay the accompaniments alongside or directly on top — garlic is placed generously, not sparingly; its pungency is structural to the Tosa style, not a garnish. Pour ponzu liberally over the slices at the table. The acid begins to whiten the outermost raw surface in the bowl: serve at once.