From Tempura to Castella: The Culinary Legacy of the Nanban

I

The Deepest Kind of Influence

Visitors leave many things behind when they go, ideas, grudges, loan words, the occasional illegitimate child. The Portuguese left Japan all of these. But they also left something infinitely harder to eradicate than a religion or a trade route: they left recipes.

The Tokugawa shogunate spent four decades hunting down missionaries, torturing converts, expelling merchants, and sealing the archipelago from Catholic contact with ruthless efficiency. They destroyed churches, burned books, confiscated printing presses.

They did not manage to get rid of the sponge cake.

Today, some of the foods most fiercely identified as Japanese, foods that appear in tea ceremonies, in New Year celebrations, on street carts, in the lunch boxes of schoolchildren, trace their origins to sixteenth-century Portuguese kitchens. Their foreign provenance has been so thoroughly absorbed, so completely naturalised, that most of the people who eat them daily have no idea they are consuming the culinary residue of the Nanban period. The Portuguese came, the Portuguese were expelled, and the cake stayed.

II

The Cake from Castile

The most celebrated of Nagasaki's Portuguese inheritances began its life as a survival ration.

Pão de ló, Portuguese sponge cake, made from eggs, sugar, and flour, was a staple aboard the carracks that sailed the trade routes between Lisbon, Goa, Malacca, Macau, and Nagasaki. It kept well, it travelled well, and it provided dense calories to men who spent months at sea eating hardtack and salt pork. It was fuel, not delicacy.

The Jesuits recognised its diplomatic potential. Sugar was rare in Japan. European confections were exotic. A gift of sponge cake to a daimyō or a prospective convert was a small luxury that carried an outsized message: we come from a world of abundance. When the Japanese asked what this golden, sweet, unfamiliar thing was called, the missionaries replied that it was bolo de Castela, cake from Castile, the Spanish kingdom. The Japanese rendered this as kasutera, and a four-hundred-year culinary tradition was born.

The transformation from Portuguese ration to Japanese icon happened in stages, and each stage involved a characteristically Japanese act of subtraction and refinement. The first thing to go was the dairy. Traditional Japanese cuisine had no butter, no milk, no cream, the entire bovine dairy complex that underpinned European baking was absent. Japanese bakers replaced the lost fats with mizuame, a thick glutinous starch syrup that gave the cake a moist, elastic, almost bouncy texture entirely unlike anything in the European original. They sprinkled coarse sugar crystals, zarame, at the bottom of the baking frame, adding a distinctive crunch. They switched from low-gluten cake flour to high-protein bread flour, creating a denser, more resilient crumb. And they baked the cake not in metal ovens, which they lacked, but in bottomless wooden frames of magnolia, maki-waku, whose low thermal conductivity produced a slow, even heat that cooked the batter without forming a hard crust.

The result was a confection that a sixteenth-century Portuguese sailor would barely have recognised. It was softer, moister, more delicate, more intentional. It was, in the Japanese sense, refined, stripped of its European roughness and rebuilt according to an aesthetic that prised subtlety over richness.

Three Nagasaki bakeries became the custodians of this tradition. Fukusaya, founded in 1624, while the Portuguese were still in Japan, is the oldest, its founder reputedly taught the recipe by a Portuguese visitor. The batter is still mixed entirely by hand. Shōōken, established in 1681, perfected gosan-yaki, a premium version made with a higher ratio of egg yolks to whites, producing an exceptionally rich, fragrant cake. Bunmeido, a relative newcomer founded in 1900, accomplished something arguably more important than perfecting the recipe: it made castella famous nationwide, largely through a 1960s television commercial featuring dancing kitten puppets that became one of the most beloved advertisements in Japanese history.

The final mark of naturalisation came when kasutera was officially classified not as yōgashi, Western confectionery, but as wagashi, a traditional Japanese sweet, specifically within the subcategory of nanban-gashi (foreign-influenced sweets). It became a standard accompaniment to matcha in the tea ceremony, its subtle sweetness perfectly calibrated to offset the bitterness of the powdered green tea. It was served by the Tokugawa shogunate to imperial envoys. It was offered to Commodore Perry when he arrived with his Black Ships in 1854, demanding that Japan open its doors to the very civilisation whose cake the Japanese had already quietly perfected.

III

What the Priests Ate on Fridays

The word tempura comes from the Latin tempora, by way of the Portuguese têmpora, a reference to the Ember Days, the quarterly periods of fasting in the Catholic liturgical calendar when the consumption of meat was forbidden. During these periods, the Portuguese community in Nagasaki prepared battered and deep-fried vegetables and fish, a practical solution to a religious obligation that had the incidental virtue of being delicious.

The dish they cooked was a version of peixinhos da horta, “little fishes from the garden”, green beans, peppers, or squash coated in a heavy wheat-flour batter and fried in lard or olive oil. It was thick, doughy, filling, and built to last. The batter was essentially a preservation technology: a dense coating that sealed the food inside and kept it edible during long sea voyages. It was not elegant. It was not intended to be.

The Japanese transformation of this heavy, practical European dish into one of the most refined expressions of their culinary tradition is a masterclass in the art of doing less.

The first change was the fat. As the cooking technique moved from the Portuguese community in Nagasaki into Japanese kitchens, and particularly as it migrated north toward Kyoto and Osaka, where Buddhist vegetarian cuisine (shōjin ryōri) exerted a powerful influence, lard and olive oil gave way to vegetable oils. The shift was theological in origin but gastronomic in consequence: vegetable oil produced a lighter, cleaner fry.

The second change was the batter. Japanese cooks, whether by instinct or by experimentation, discovered that the key to a lighter coating was the deliberate under-development of gluten. They switched to soft, low-protein wheat flour. They used ice-cold water instead of room-temperature liquid. And, crucially, they mixed the batter as little as possible, leaving visible lumps and streaks of dry flour. Every instinct of a European baker screamed that this was wrong. It was, in fact, the single most important technical innovation in the history of the dish: the unmixed, gluten-inhibited batter produced a coating so thin, so crisp, so impossibly light that it shattered at the touch of chopsticks, the signature saku saku texture that defines modern tempura.

Where the Portuguese batter smothered, the Japanese batter revealed. The ingredient inside, a prawn, a shiso leaf, a slice of lotus root, was the point. The coating was a translucent shell through which the natural colour of the food remained visible. The frying was a technique of steam-cooking: the moisture inside the ingredient turned to vapour inside the sealed batter, cooking the food from within while the exterior crisped in the oil. The result was a morsel that was simultaneously fried and fresh, hot, crisp, and intensely flavoured by the ingredient itself rather than by the coating.

Because the batter was now essentially unflavoured, no seasoning, no herbs, no spice, the Japanese developed tentsuyu, a dipping sauce of dashi, soy sauce, and mirin, served with grated daikon radish and ginger whose enzymes aid in digesting the oil. The sauce completed the dish: the crisp shell, the steamed interior, the savoury-sweet dip, the sharp bite of radish. Every element served a specific purpose. Nothing was decorative.

Tempura's democratisation happened during the Edo period, driven by an agricultural revolution in oil production. Deep-frying had been a luxury in Japan because cooking oil, traditionally pressed from perilla seeds, was scarce and expensive, reserved primarily for lamp fuel and medicine. The mass cultivation of rapeseed changed everything, producing cheap, stable, high-temperature oil in quantities that made frying accessible to ordinary cooks. In the capital of Edo, where strict fire codes banned indoor deep-frying in the city's densely packed wooden buildings, tempura became the ultimate street food, sold at outdoor stalls called yatai, served on bamboo skewers, fried in toasted sesame oil that gave Edo-style tempura its characteristic golden colour and nutty aroma.

The Portuguese Ember Day fast had become Japanese fast food.

IV

The Sweet That Charmed a Warlord

In 1569, the Jesuit historian Luís Fróis secured an audience with Oda Nobunaga, the most powerful and most dangerous man in Japan, and presented him with a glass flask of konpeitō.

The gift was calculated. Sugar was vanishingly rare in sixteenth-century Japan. Refined sugar confections were objects of wonder. Nobunaga, who collected curiosities the way he collected enemies, was delighted. The small, star-shaped candies, their name derived from the Portuguese confeito, became one of the incidental instruments of Jesuit diplomacy, a sweet opening gambit in the long negotiation between European missionaries and Japanese power.

Konpeitō is produced by a process so slow and so labour-intensive that it borders on meditation. A core of coarse sugar is placed in a heated, rotating, gong-shaped drum. Sugar syrup is ladled over the cores repeatedly, for up to two weeks, as the drum turns. The distinctive crystalline spikes that give konpeitō its star shape form organically through the uneven accumulation of sugar layers, a process that cannot be replicated by machine or mould. Each spike is an accident of physics, which means each candy is unique.

The confection survived the Portuguese expulsion, the sakoku centuries, and the Meiji modernisation to become one of the most symbolically charged sweets in Japanese culture. The Imperial Household uses konpeitō as an official welcome gift, presented in ornate bonbonnière boxes to visiting dignitaries. A candy that arrived in a Jesuit's luggage now represents the Japanese state.

V

The Full Pantry

Castella, tempura, and konpeitō are the headline acts, but the Portuguese culinary legacy in Japan runs much deeper, a full pantry of dishes, techniques, and ingredients that survive in forms their originators would find unrecognisable.

Pan, the Japanese word for bread, comes directly from the Portuguese pão. Japan had no bread-baking tradition before the missionaries arrived. The word survived the expulsion, outlasted two centuries of isolation, and was waiting, ready-made, when bread returned to Japan during the Meiji era. Every pan-ya (bakery) in the country is linguistically a Portuguese shop.

Nanbanzuke, literally “Southern Barbarian pickle”, is the Japanese descendant of escabeche, the Portuguese and Spanish technique of preserving fried fish in vinegar. The Japanese version substitutes rice vinegar, soy sauce, and mirin for wine vinegar, creating a marinade that is distinctly local while remaining structurally identical to its Iberian ancestor. The technique also laid the groundwork for chikin nanban, fried chicken in sweet vinegar with tartar sauce, which is today one of the most popular comfort foods in Japan, a regional specialty of Miyazaki Prefecture that has conquered the national palate.

Keiran sōmen, “chicken egg angel hair”, is a direct descendant of the Portuguese fios de ovos, golden egg threads created by drizzling beaten yolks into boiling sugar syrup. The technique produces impossibly delicate strands of sweet egg that look like edible silk. It is a dish that has travelled the entire Portuguese maritime network, from Portugal to Brazil to Thailand (where it is known as foi thong) to Japan, acquiring local variations at every stop while remaining, in its essence, the same act of culinary alchemy.

Hiryōzu, deep-fried tofu fritters mixed with vegetables, takes its name from the Portuguese filhós, a sweet fried dough. The connection is one of appearance rather than flavour: the Japanese cooks who first prepared the tofu fritters thought the finished product resembled the Portuguese pastry and borrowed the name. The dish itself is entirely Japanese. The word is entirely Portuguese. This kind of linguistic fossil, a foreign name attached to a local creation, is one of the most characteristic marks of the Nanban exchange.

Hikado, a Nagasaki stew of diced vegetables, chicken, and fish simmered in dashi and thickened with grated sweet potato, derives from the Portuguese picado (“chopped”). It is one of the few surviving Nanban dishes that retains an identifiably Portuguese structural logic: a one-pot meal of small-cut ingredients in broth, adapted to Japanese flavours through the use of dashi and sweet potato rather than the European stock and root vegetables of the original.

And then there are the crops. Kabocha, the Japanese pumpkin that is ubiquitous in home cooking, in tempura, in soups, in the nimono simmered dishes that anchor everyday meals, arrived via Portuguese sailors who brought it from Cambodia, which is how the squash acquired its name (Camboja in Portuguese, rendered as kabocha in Japanese). Chilli peppers, native to the Americas, reached Japan through Portuguese trade networks and became an essential ingredient in shichimi tōgarashi, the seven-spice blend that sits on every ramen counter in the country.

VI

The Root That Saved Millions

The most consequential Portuguese culinary introduction to Japan was not a recipe. It was a tuber.

The sweet potato, native to Central and South America, reached Asia through the Portuguese maritime network, travelling from the New World to the Philippines, from the Philippines to China, and from China to the Ryūkyū Kingdom (modern Okinawa), where it arrived in the early seventeenth century. From Ryūkyū it crossed to the Satsuma domain on the southern tip of Kyushu, where the warm climate and volcanic soil proved ideal for its cultivation. The crop became so associated with the domain that it acquired the name it still carries: satsuma-imo, the Satsuma potato.

Sweet potatoes grow in poor soil. They tolerate drought. They produce calories with a reliability that rice, which requires flooded paddies, predictable rainfall, and intensive labour, cannot match. These qualities made the sweet potato a famine crop of extraordinary importance.

During the Kyōhō Famine of 1732, when locust plagues devastated rice harvests across western Japan, the Satsuma domain was partially spared because its farmers had diversified into sweet potato cultivation. The lesson was not lost on the shogunate. In 1735, a scholar named Aoki Konyō presented a treatise on the sweet potato to the eighth shogun, Tokugawa Yoshimune, arguing that the crop should be cultivated nationally as insurance against famine. Yoshimune appointed Konyō as an official sweet potato commissioner, earning the scholar the affectionate nickname “Professor Sweet Potato”, and authorised experimental cultivation at the Koishikawa Botanical Garden in Edo. The experiments succeeded. Sweet potato cultivation spread across the country.

When the Tenmei Famine struck in the 1780s, the sweet potato served again as a critical lifeline for populations that would otherwise have starved. A crop that had arrived in Asia in the hold of a Portuguese ship became, within two centuries, one of the most important foods in the Japanese agricultural system, a bulwark against the catastrophic harvest failures that periodically threatened a rice-dependent civilisation.

VII

The Art of Forgetting

The most remarkable thing about the Nanban culinary legacy is how completely it has been assimilated.

Kasutera is not thought of as Portuguese. It is thought of as Nagasaki's. Tempura is not considered a foreign import. It is considered a quintessence of Japanese culinary philosophy, the art of revealing an ingredient's nature through the lightest possible intervention. Konpeitō is not remembered as a Jesuit diplomatic tool. It is an imperial gift. Pan is not heard as a Portuguese word. It is simply the word for bread.

In 2013, UNESCO inscribed Washoku, traditional Japanese dietary culture, on its Representative List of the Intangible Cultural Heritage of Humanity, recognising its respect for nature, its nutritional balance, and its deep cultural traditions. Tempura, a dish that exists because sixteenth-century Portuguese Catholics were not allowed to eat meat on Ember Days, is one of the foods the inscription celebrates.

The Tokugawa shogunate expelled the Portuguese, banned their religion, destroyed their churches, and sealed Japan from Catholic contact for over two centuries. The sponge cake, the fried batter, the sugar candy, the bread, the pumpkin, the chilli pepper, and the sweet potato stayed.