Sauce Robert

Sauce Robert is a brown mustard sauce and one of the small sauces, or compound sauces, derived from the classic French demi-glace, which in turn is derived from espagnole sauce, one of the five mother sauces in French cuisine . Sauce Robert is made from chopped onions cooked in butter without color, a reduction of white wine, pepper, an addition of demi-glace and is finished with mustard. It is suited to red meat, specifically pork, typically grilled pork.

Source: Wikipedia