In most Japanese supermarkets, sweet cream butter, or muhakkō batā dominates the shelves, but in recent years cultured butter, hakkō batā — a type of butter common in continental Europe — can be found in upscale supermarkets such as Seijo Ishii, due to the popularity of Echire butter, a French butter considered the best in the world. The smoothness of the butter makes it a popular choice for patissiers.

The brand's Tokyo shop in Marunouchi, Echire Maison du Beurre, opened five years ago primarily to sell Echire butter at ¥363 for 30 grams.

So popular is the butter, a line gathers outside Echire Maison du Beurre an hour before it opens on weekdays. The store's light croissants, made only with Echire butter, sell out by noon, and customers trying to get their hands on the Gateau Echire Nature, a butter cake (¥4,320) shaped like blocks of butter pressed from traditional wooden molds, have to be quick: The store only bakes a limited amount — a number that the brand manager wouldn't divulge — each day.