What is "espagnole sauce"

In cooking, espagnole sauce is one of Auguste Escoffier's five mother sauces that are the basis of sauce-making in classic French cooking. These types of sauce were already gathered in different Spanish cooking handbooks of the late 19th century. Escoffier popularized the recipe, which is still followed today.

Espagnole has a strong taste and is rarely used directly on food. As a mother sauce it serves as the starting point for many derivatives, such as Sauce Africaine, Sauce Bigarade, Sauce Bourguignonne, sauce aux champignons, sauce charcutière, sauce chasseur, Sauce Chevreuil and demi-glace. There are hundreds of other derivatives in the classical French repertoire.

Escoffier included a recipe for a Lenten espagnole sauce, using fish stock and mushrooms, in Le Guide culinaire, but doubted its necessity.