Two pieces of castella
A boxed castella, usually given as a gift
A shop selling boxes of castella
Nagasaki sponge cake
Castella is a sweet yellow sponge cake, known in Japan as a specialty of Nagasaki.
A cake of Portuguese origin, castella was quickly adopted by the Japanese.
Before the sakoku, seclusion of Japan (1641-1853), Nagasaki was a busy international trade port. A Portuguese boat arrived one day at the port of Hirado, in Nagasaki prefecture. The Christian missionaries aboard offered an unknown cake to a local in exchange for permission to dock and spread their holy word among the inhabitants.
At first this mysterious new cake, castella, was reserved only for the rich, but it quickly spread throughout the country thanks to the tea ceremony, a cultural phenomenon that was growing in popularity at the time.
The ingredients of castella are simple (eggs, flour and sugar), but sugar was rare in ancient Japan. However, the recipe was gradually adapted by the Japanese, facilitated by the absence of dairy products, and mizu ame (水飴), a starch syrup commonly used in Japan, was added, which gives castella its firm texture, which is why the cake is categorized as wagashi, a Japanese sweet.
Where does the name castella come from?
A missionary introduced this cake as "bread of Castile", a Spanish kingdom at the time. Castile became castella (kasutera with Japanese pronunciation). However it's actually closer to Pao de Lo, a kind of traditional Portuguese sponge cake, the true origin of castella.
Its ingredients include eggs, flour and sugar. It was the Portuguese who introduced refined sugar to Japan, therefore castella is classified as a nanban-gashi (南蛮菓子), a cake or sweet introduced from Portugal in the sixteenth century, as many other sweets were at the time, such as the multi-colored konpeito candies and cookies.
Finding castella in Japan
It's very easy to find castella in depa-chika, airports, and main train stations. The Japanese often buy it as a gift, well presented in a beautiful box as if it were the finest of delicacies. Today it can be found in various flavors like chocolate or matcha.
If you're in Nagasaki, go to Fukusaya, a shop founded in 1624, a pioneer of this nanban-gashi! A 10-piece castella cake is sold for 1,000 yen ($8) and can be stored for 8 to 10 days at room temperature.