Founded in 1866 and run by the same family ever since, Yossou specialises in chawanmushi — a steamed savoury egg custard usually served in Japan as a small side dish, but here scaled up to a meal in its own right. The Yossou version is a deep porcelain cup studded with eel, prawn, ginkgo nut, and chicken, paired with a bowl of mushi-zushi (steamed sushi rice). The Western-influenced Nagasaki habit of treating chawanmushi as a main course is a quirk you only encounter here. The restaurant occupies a serene wooden building five minutes' walk from Hamanmachi Arcade.