Espagnole Sauce is the foundation of all of the brown sauces. A number of modifications have been made of this sauce since its conception. The sauce is now made of a rich brown veal stock thickened with a brown roux. The sauce is then simmered with a mirepoix, bouquet garni, and wine. The long, slow cooking help to purify and concentrate its flavour. It is finally strained through very fine muslin. Demi-glace and glace de viande are all structured around a fine Espagnole sauce.