When the Bourbons made their way to the Spanish throne under Louis XV, and when Spanish fashions came back to Paris, the French cooks took a hint from the Spanish pot-au-feu—the olla podrida—and produced a variation of their brown sauce which they called "Spanish". The essential principle of the French pot-au-feu was beef; the essential principle of the Spanish was bacon, ham, the red Estremadura sausage—all well smoked. . . The Duc de St. Simon sent home marvellous accounts of the hams of Montanches; there grew up a rage for Spanish hams; and the French were not to blame, for they have no hams of their own which have any reputation. Great as they are in pig's flesh, they are poor hands at bacon and ham; and the treasures of Montanches were a revelation to them. They ran wild after ham. . . And so, by introducing the flavour of the Estremadura bacon and ham into the old brown sauce of the French, there came into being the Spanish sauce. . . The hams of Montanches are not too plentiful in this world of sorrow, and the cooks came to be satisfied with any ham—even with French ham, which is little better than salted pork. So the meaning of the prescription was lost; the peculiarity of the Spanish sauce passed away, and its name became a puzzle.
Espagnole sauce ( French pronunciation: [ɛspaɲɔl] ) is a basic brown sauce, and is one of Auguste Escoffier 's five mother sauces of classic French cooking . This sauce was already compiled in different Spanish cooking handbooks of the late 19th century,  and Escoffier popularized the recipe, which is still followed today.