The first time I grilled fresh unagi — live eel, killed that morning, butterflied by hand and lacquered with a tare I'd been reducing all week — I genuinely didn't know what I was eating. I'd worked with frozen kabayaki hundreds of times. I knew what unagi tasted like. Except I didn't. Not really.
Frozen unagi is fine. I'll say that upfront, because this post isn't a takedown of a product that feeds millions of people and makes a genuinely difficult dish accessible. The frozen, pre-glazed kabayaki you pull from a vacuum pack, score, and reheat is convenient, consistent, and honestly not bad. It's what roughly 95% of the unagi served in restaurants worldwide — including many in Japan — actually is.
But fresh unagi, prepared from a live eel and grilled properly with real tare, is a different food. The fat renders differently, the texture has a yielding quality that freezing simply can't survive, and the way a well-made tare caramelises against freshly scored flesh is something you remember. The trade-off is real: preparing live eel is one of the more genuinely unpleasant tasks in a Japanese kitchen. This post covers the full picture — what each version actually is, how to handle both well, and where to find fresh eel if you're in Europe and want to try.
Unagi in Japanese Cuisine: Why This Fish Has Its Own Day
Unagi — Anguilla japonica, the Japanese freshwater eel — has been eaten in Japan for over a thousand years. It appears in the eighth-century poetry anthology Man'yoshu, and by the Edo period (1603–1868) specialist unagi restaurants, called unagiya, had become a fixture of Tokyo's street food culture. This is not a trendy ingredient. It carries the kind of cultural weight in Japan that oysters carry in France.
The centrepiece of unagi's cultural calendar is Doyo no Ushi no Hi — the "midsummer day of the ox," which falls in late July or early August according to the traditional Japanese calendar. On this day, eating unagi is considered essential for stamina in the summer heat. The custom reportedly dates to the eighteenth century, when a struggling eel vendor, on the advice of polymath Hiraga Gennai, placed a sign claiming that eating unagi on this date provided vital energy. Whether or not the science holds up, the tradition stuck hard. Japan consumes roughly 70% of its annual unagi supply around Doyo no Ushi no Hi. Supermarkets sell out. Unagiya have queues.
The classic presentation is unaju (うな重) — a lacquered wooden box filled with steamed rice, topped with sliced kabayaki (grilled, glazed eel), with a small pot of extra tare on the side. Simpler versions come as unadon, the same thing in a ceramic bowl — the donburi format. Shirayaki (白焼き) is unagi grilled without any glaze, served with wasabi and soy — the purist version that lets the fat and smoke speak for themselves.
Understanding this context matters when you're evaluating fresh vs frozen unagi. You're not just comparing two preparations of a fish. You're dealing with an ingredient that has centuries of culinary tradition behind it.
How Most Unagi Reaches Your Plate: The Frozen Supply Chain
Here is the honest supply chain story, told without alarmism.
Japan has a wild eel problem. Anguilla japonica is critically endangered. Wild catches have declined by more than 90% since the 1960s due to overfishing, habitat loss, and changes to river systems. Japan still depends almost entirely on wild-caught juvenile eels — called shirasu, or glass eels — as the basis for aquaculture, because no one has cracked commercial eel breeding in captivity at scale. These juveniles are caught in rivers, transferred to farms, grown out over 12–18 months, and harvested.
The economics pushed most of this production to China. Chinese aquaculture now accounts for the overwhelming majority of unagi consumed in Japan, the EU, and North America. The eel is grown out in large inland tanks, harvested, then processed on-site: killed, butterflied, blanched, grilled, glazed with a standardised tare, steamed, and vacuum-packed. The resulting kabayaki is flash-frozen and shipped.
This product is not a shortcut or a compromise born of laziness. It is a genuinely complex piece of food manufacturing, and when it's done well — by reputable producers in Zhejiang or Fujian province — the result is a consistent, palatable product. The tare tends to be sweeter and more one-dimensional than a properly reduced house tare, the texture is softer than it should be due to the freeze-thaw cycle, and the smoke is minimal or absent. But it eats reasonably well, it's safe, and it's what most people have in mind when they say they love unagi.
Where things vary is quality control and sourcing transparency. The better Japanese importers — brands you'll see in specialist Asian supermarkets — are more stringent about provenance and processing standards than commodity product. If you're buying frozen unagi, it's worth paying for the Japanese-branded product rather than the generic equivalent.
What Fresh Unagi Actually Tastes Like — and How It's Prepared
The fresh vs frozen unagi difference is not subtle once you've experienced both.
Texture. Freezing breaks down cell walls. Frozen kabayaki, once reheated, has a soft, slightly spongy interior with a thin caramelised crust. Fresh-grilled unagi has distinct layers of texture: the skin crisps properly, the outer flesh develops a light crust from direct heat, and the interior stays moist and almost custardy — yielding without being soft. The fat in fresh eel renders gradually through grilling rather than being cooked out and locked in by freezing; you taste it as richness that coats your palate rather than oiliness.
Tare absorption. Frozen kabayaki arrives pre-glazed. You're reheating and optionally adding more tare. Fresh eel, scored and grilled, absorbs tare differently — the cuts open up, the glaze penetrates the flesh with each pass over the grill, building in layers. The caramelisation you get from raw tare meeting a hot grill is not the same as reheated glaze.
Smoke. Authentic binchotan charcoal grilling produces a faint, clean smokiness that is part of the flavour of properly made kabayaki. Frozen product processed industrially has no smoke character. Even grilling frozen kabayaki at home on a charcoal grill won't replicate this — the flesh has already been cooked through. Fresh eel, raw flesh meeting real smoke, is a different proposition.
Preparation of fresh eel. I'll be direct: this is not fun. The traditional method begins with ikejime — a precise kill technique involving a spike through the brain to immediately neutralise the nervous system, followed by severing the spinal cord. This matters because eel continues to move after conventional killing and the muscle tension affects texture. If you've never ikejime'd an eel, the physical reality of it — a live, muscular fish with significant writhing force — is something to mentally prepare for. Many home cooks stop here and decide frozen is fine. That is a completely rational decision.
After ikejime, the eel is nailed through the head to a board (the traditional tool is an eel spike, called a me-uchi), then butterflied from the back using a dedicated eel knife — the unagisaki bōchō, which has a blade shaped specifically for this cut. The knife follows the spine cleanly from head to tail, opening the eel flat without tearing the flesh. A sharp, medium-weight knife — a deba works if you don't have a dedicated unagi knife — will do the job, but the cut requires confidence and a good edge. This is one of those tasks where a blunt knife makes an unpleasant job genuinely difficult.
Kanto vs Kansai: The Two Schools of Unagi Preparation
This is one of the more genuinely interesting fault lines in Japanese culinary culture, and it's directly relevant to understanding what you're tasting.
Kanto style (Tokyo and surrounds) is the method you encounter most often in formal unagiya. After butterflying, the eel is cut into portions and skewered. It's grilled briefly over charcoal — just long enough to firm the exterior — then steamed for 20–30 minutes until the interior is fully cooked and the fat has rendered evenly. Then it goes back on the grill for a final round of tare application and caramelisation. The steaming step makes Kanto-style kabayaki notably tender, almost pillowy, and removes some of the excess fat. The result is mild, extremely soft, and the tare flavour is prominent.
Kansai style (Osaka, Kyoto) skips the steaming entirely. The eel is butterflied from the belly rather than the back, then grilled directly from raw to finished product — tare applied progressively as it cooks. The result has more textural character, more pronounced fat, and a more assertive smoke flavour. If Kanto-style unagi is like a very tender braise, Kansai-style is closer to grilled fish. Both are legitimate; they're expressing different values about what makes the ingredient good.
For home cooks attempting fresh eel, Kansai style is more accessible — it requires only a grill and a good tare. Kanto style needs a steaming setup that can handle the portions after initial grilling, which adds complexity.
Making tare at home. Tare is the lacquering sauce applied during grilling — a reduction of soy sauce, mirin, sake, and sugar, with a small amount of the previous batch carried over each time (in specialist restaurants, the tare pot is decades old). A simplified version that works well at home:
- 120ml soy sauce (use a good-quality regular soy, not low-sodium)
- 120ml mirin
- 60ml sake
- 1 tablespoon sugar
Combine in a small saucepan, bring to a simmer, and reduce by roughly a third until it coats a spoon. Cool completely before using. It should be glossy, slightly thick, and sweet-savoury. Apply to the grilling eel in three or four passes, letting each coat caramelise before adding the next.
Getting the Most from Frozen Unagi at Home
Since frozen kabayaki is what most people are actually cooking, here's how to handle it so it performs as well as it can.
Don't microwave it. I know the packet says you can. Microwaving steams the eel in its own moisture and makes the texture rubbery. You want radiant heat.
Oven method (most reliable): Preheat to 200°C. Remove the eel from the vacuum pack and place skin-side down on a lined baking tray. Brush generously with additional tare (homemade or bottled). Bake for 10–12 minutes until heated through and the glaze is bubbling at the edges. For extra caramelisation, finish under a hot grill for 2–3 minutes — watch it closely, the sugar in the tare burns fast.
Pan method (quicker): Score the flesh lightly in a crosshatch pattern with a sharp knife — this helps additional tare penetrate and speeds heat transfer. Heat a dry non-stick pan over medium-high heat. Place the eel flesh-side down first for 2 minutes, then skin-side for 2 minutes. Add a tablespoon of tare and let it caramelise around the eel for 30 seconds. This is the fastest way to get reasonable caramelisation on frozen product.
The tare matters more than you think. The pre-applied glaze on frozen kabayaki is usually quite sweet and relatively thin. Adding a good homemade tare during reheating — rather than serving it on the side — makes a meaningful difference to the final dish. The added tare integrates with the heat in a way that post-service application doesn't replicate.
Rest before serving. Let the reheated eel sit for 2 minutes before serving. This lets the fat redistribute and the glaze set slightly. Serve over freshly made short-grain rice that's been kept warm and is not overly sticky.
Where to Find Fresh Eel in Europe
Fresh, live eel is genuinely available in Europe if you know where to look — though it takes some effort.
Specialist Japanese importers. The most reliable route. Companies like Atariya Foods (UK), Ichiba (UK), and Umami (various European cities) occasionally carry fresh or live eel, typically on request and in advance. Emailing ahead is essential — this is not a walk-in purchase.
Dutch and Belgian live eel suppliers. The Netherlands has a significant eel farming industry (European eel, Anguilla anguilla, rather than Japanese eel — the flavour and fat profile are slightly different but the preparation is identical). Dutch fishmongers and specialist aquaculture suppliers can supply live eel, and the quality is genuinely good. Search for "paling" (the Dutch term for eel) via specialist fishmongers in major cities.
Asian wet markets. In cities with large Chinese or Vietnamese communities — London, Paris, Amsterdam, Brussels — wet markets and larger Asian supermarkets sometimes hold live eel in tanks. These are almost certainly Chinese farmed eel (Anguilla japonica or A. bicolor), which is exactly what you'd want for kabayaki.
Fishmongers with game and specialist fish. A good traditional fishmonger in the UK or France will sometimes carry whole fresh eel from local river fisheries. The seasonality is real — late summer through autumn is peak. Call ahead, specify that you want it alive or freshly killed (not smoked — European smoked eel is a different product entirely).
One note on species: European eel (Anguilla anguilla) is critically endangered and under strict fishing quotas. If you're sourcing eel in Europe, farmed is the right choice on conservation grounds. Farmed product — whether from the Netherlands, Denmark, or China — is a more defensible purchase than wild-caught European eel.
On the knives. Breaking down a whole fresh eel properly is one of those tasks where the right knife makes a visible difference. A deba (出刃包丁) — the single-bevel Japanese cleaver designed for breaking down whole fish — handles the initial skull work and spine removal with control that a Western chef's knife can't quite match. If you're doing this at home and want to invest in the knife that earns its place across all whole-fish prep, a mid-weight deba is where I'd start. Smart Sushi Chef carries deba knives across a range of weights — the 165mm version is the most versatile for eel and medium fish work.
Frequently Asked Questions About Unagi
Q: What is the difference between fresh and frozen unagi? A: Fresh unagi is prepared from a live eel — killed, butterflied, and grilled with tare on the day. The texture has distinct layers, the fat renders during cooking rather than being locked in by freezing, and tare caramelises against raw flesh for a more complex glaze. Frozen kabayaki is pre-cooked and glazed before freezing; it's convenient and consistent, but the texture is softer and the flavour less vivid than fresh.
Q: What is kabayaki eel and how is it different from regular unagi sushi? A: Kabayaki (蒲焼き) is a specific preparation — the eel is butterflied, skewered, and grilled with repeated applications of a sweet soy-based tare sauce. It's the form unagi almost always takes when served as unaju or unadon. Unagi sushi (nigiri) uses the same kabayaki preparation, sliced and placed over rice with an additional brush of tare. The distinction is presentation, not the eel itself.
Q: Is the unagi served at most restaurants fresh or frozen? A: In the overwhelming majority of cases — including many specialist restaurants in Japan, and virtually all unagi served outside Japan — it is frozen pre-glazed kabayaki, typically imported from Chinese aquaculture facilities. This is not a dirty secret; the product is genuinely functional. Fresh-grilled unagi from live eel is reserved for dedicated unagiya with access to live supply, which is a small minority of restaurants globally.
Q: What is the difference between unagi and anago? A: Unagi is Japanese freshwater eel (Anguilla japonica); anago is saltwater conger eel (Conger myriaster). They are different species. Anago is leaner, more delicate in flavour, and traditionally served simmered rather than grilled — it's common as nigiri sushi where unagi is typically served in a bowl. Unagi has significantly more fat and a more pronounced, rich flavour. Anago is more forgiving to work with; it doesn't have the same writhing challenge as live freshwater eel.
Q: Can I prepare fresh eel at home if I've never done it before? A: Yes, but go in with realistic expectations. The ikejime kill requires a degree of nerve and a sharp, stiff spike — watching it done on video before attempting it yourself is not optional. The butterflying cut is genuinely manageable with a sharp deba or medium-weight knife, once the eel is nailed to a board. The rest of the process — scoring, grilling, tare application — is well within a confident home cook's reach. The difficulty is the initial 10 minutes, not the cooking.
Q: What is tare sauce and how do I make it for unagi? A: Tare (タレ) is the thick, sweet-savoury glazing sauce applied during grilling — the defining flavour of kabayaki. It's a reduction of soy sauce, mirin, sake, and sugar. A basic home version: combine 120ml soy, 120ml mirin, 60ml sake, and 1 tablespoon of sugar in a pan, simmer and reduce by a third until glossy and coating. Apply to the eel in multiple passes during grilling, letting each coat caramelise before adding the next. In specialist unagiya, the same tare pot is maintained and topped up over years or decades — the depth of flavour that builds over time is part of what makes those restaurants special.