Sauce Robert is a classic French sauce made from a base of brown sauce or Espagnole sauce. It is typically flavored with onions, white wine, and mustard, giving it a rich and savory taste. This sauce is often used to accompany meats, particularly grilled or roasted dishes. Traditionally, Sauce Robert is prepared by sautéing onions in fat, deglazing the pan with white wine, and then adding the brown sauce. It is then simmered until it thickens slightly. This sauce is a staple in French cuisine and is appreciated for its versatility and depth of flavor.