'Espagnole' is a basic sauce of which cuisine?

Espagnole sauce is a basic brown sauce, and is one of Auguste Escoffier's five mother sauces of classic French cooking. Escoffier popularized the recipe, and his version is still followed today.

Georges Auguste Escoffier was a French chef, restaurateur and culinary writer who popularized and updated traditional French cooking methods.

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.

The basic method of making espagnole is to prepare a very dark brown roux, to which brown stock (stock made from simmering roasted bones, meats and aromatics) is added, along with roasted bones, pieces of beef, vegetables, brown sugar and various seasonings. This blend is allowed to slowly reduce while being frequently skimmed.