Hollandaise sauce is an emulsion of lemon and butter with egg yolk being the key ingredient and is a French sauce believed to have mimicked a Dutch sauce.French sauces date back to Medieval times, but hollandaise originally did not include egg yolks but instead was emulsified with butter. Hollandaise features highly in 19th and 20th century classic French cookery, as well as cooking today.
The French have a base sauce or "Mother Sauce", which four different sauces derive from. This was classified by the 19th century chef Antonin Careme and comprised of Bechamel, Espagnole, Veloute and Allemande. Each a variation of the classic white sauce either thickened by a roux or egg yolks and cream. Each of these sauces can be used as a base with extra ingredients added to create more sauces such as Morney (with cheese), Bordelaise (with red wine and beef marrow).
In the early part of last century various other sauces began to emerge with the same classifications including tomato sauce, mayonnaise and various butter sauces. To make sauce aux capres you can add drained capers, maltaise sauce has the addition of blood oranges, chantilly/mousseline sauce has whipped cream and moutarde is made with the addition of Dijon mustard.
