Why Knife Work Defines Sashimi

A generous piece of sashimi-grade tuna can be undone in a single careless stroke. Equally, a modest fillet of mackerel handled with real skill can look and taste as though it came from a counter in Tokyo. On our Japanese culinary tuition days, this is the lesson that lands hardest: flavour in raw fish is partly chemistry, but presentation is entirely craft. Guests eat with their eyes long before their chopsticks arrive, and a ragged, bruised slice that weeps moisture tells them instantly that something is off.

The reassuring news is that the three techniques below are learnable. They ask for patience, a genuinely sharp knife and a willingness to slow right down — but they will change how a plate of raw fish reads to the person sitting in front of it.

Sharpness, Steel and Stance Come First

No technique rescues a dull blade. A blunt edge tears muscle fibres instead of severing them, leaving a cloudy, oxidised surface and a texture that eats stringy rather than silky. Before you attempt anything decorative, sort out your kit and your posture.

• The knife: a yanagiba is the traditional sashimi blade — long, single-bevel and designed for one clean drawing cut. A sujihiki is a fine Western-style alternative for home kitchens. Keep a small, rigid paring knife for decorative work.
• The edge: sharpen on a 1000-grit stone, refine on 6000, and touch up little and often. A knife that glides through a ripe tomato without pressure is ready for fish.
• The stance: feet shoulder-width apart, blade held with a relaxed grip, the cut driven from shoulder and elbow rather than a flapping wrist. Tension in the hand produces tension in the slice.
• The temperature: work with fish at 0–2°C, taking small portions from the fridge as you go. Warm fish collapses under the blade and loses its shape within minutes.

Katsuramuki: The Rolling Cut

Katsuramuki is the Japanese rolling cut, and it is the foundation of almost every sashimi garnish you have admired. The blade stays almost still while the ingredient rotates against it, producing one continuous sheet a millimetre or two thick. Practise on cucumber first — it is cheap, forgiving and behaves beautifully.

Hold the cucumber in your guiding hand with the thumb resting lightly near the spine of the blade. Lay the knife flat against the vegetable, edge just kissing the surface, then rotate the cucumber towards you while easing the blade forward. The motion is rhythmic, not forceful. Once you can produce a full unbroken sheet, stack the sheets and shred them finely for tsuma, the nest of daikon that sits beneath the fish. Soak shredded daikon in iced water for ten minutes to crisp it and soften the bitterness, then drain thoroughly — wet garnish dilutes the plate.

Angled Slicing: The Heart of Sashimi

The angle of your blade decides the character of the slice. Each cut should be a single, continuous draw from heel to tip, never a sawing motion.

• Hira-zukuri: the standard flat slice, roughly 7–10mm thick, cut straight down across the grain. Ideal for tuna, salmon and yellowtail, where you want a clean, meaty bite.
• Usu-zukuri: a translucent, almost paper-thin slice achieved by tilting the blade to a shallow, near-horizontal angle and drawing it forward and down in one long motion. Perfect for sea bream, flounder, scallop and squid.
• Somen-zukuri: squid sliced into noodle-fine strips, which curl gently and catch a dressing beautifully.

Always cut across the grain, so the fibres stay short and the slice holds its shape on the plate. If the fish starts to cling or tear, stop and hone the edge — the fault is nearly always the knife.

Decorative Cuts and Garnish Work

Kazari, the art of decorative cutting, should whisper rather than shout. Two or three well-chosen garnishes flatter the fish; a forest of them buries it.

• Hanagata: a simple flower cut worked into a thick slice of cucumber or carrot with a small, sharp knife.
• Kikko: a tortoiseshell crosshatch scored lightly into squid, which opens into diamonds as it marinates.
• Ika no kazari: fine scoring on a squid sheet that folds into a blossom shape once dressed.

Support these with shiso leaf, finely sliced myoga, a little lemon zest or a dab of yuzu kosho. Keep a damp cloth beneath your board so nothing slides, and wipe your knife between cuts — a clean blade makes a clean edge.

Building the Plate, and Where to Learn

Arrange sashimi in odd numbers, three or five slices to a portion, overlapping like roof tiles and leaning gently to the left. Tuck a little wasabi beneath the fish rather than beside it, add your tsuma and shiso, and serve on a chilled plate — around 5–8°C is ideal, cold enough to refresh without numbing the aroma. Wipe the rim before it leaves the kitchen.

At home, buy from a fishmonger you trust and ask specifically for sashimi-grade fish. If you are preparing wild fish to eat raw, freeze it at −20°C for at least twenty-four hours first, in line with UK food safety guidance. Farmed salmon and tuna from reputable suppliers are generally handled to raw-ready standards, but always ask.

What a good course gives you is correction: someone watching your wrist, adjusting your blade angle by two degrees, and telling you when to stop practising a cut for the evening. That feedback compresses months of trial and error into a single afternoon — and it is the difference between fish that looks merely fresh and fish that looks composed.