Robert Sauce

Fry slowly in a saucepan two white onions weighing six ounces, and cut into small squares, with two ounces of butter, in such a way that they are half cooked without browning, then drain off the butter, and moisten the onions with two gills of consomme (No. 189), and one gill of white wine; reduce the sauce to a glaze, then moisten once more with three gills of espagnole sauce (No. 414), reduced with one gill of veal blond (No. 423); add a coffeespoonful of sugar, a teaspoonful of vinegar, a tablespoonful of mustard, and a pinch of cayenne; let boil for a few minutes to enable the fat to be skimmed off, and keep the sauce warm in a bain-marie.