This butter and egg emulsion is one of the five mother sauces of French cuisine, and one of the most famous sauces in western cuisine. It consists of an emulsion of egg yolks and melted or clarified butter with salt, pepper, and an acidic note added by either a splash of lemon juice or a combination of water and wine vinegar.
Although the inventor of the sauce remains unknown, some claim that hollandaise was originally invented in the Netherlands before being brought to France by the Huguenots. Other food historians claim that it was originally called Isigny, a sauce that was especially popular in Normandy, but that the name changed during World War I due to the fact that butter was scarce and had to be imported into France from the Netherlands.
The earliest mention of the sauce is found in a 1593 Dutch cookbook, and Pierre La Varenne described a similar sauce in his 1651 cookbook Le Cuisinier françois. Hollandaise sauce is most commonly used to season fish and steamed vegetables such as asparagus.