Into a pint of chicken essence (No. 387) add two tablespoonfuls of rice flour diluted in a gill of cold milk, also some salt, pepper and lemon juice, two ounces of cooked chicken cut in small squares and four chopped hard-boiled egg-yolks; work the sauce steadily, reduce properly, and add one gill of double cream, and two ounces of fresh butter.
A thickened chicken velouté enriched with cream, butter, diced chicken and sieved yolks. Ranhofer assumes you have his chicken essence already made and that the sauce will be finished to order.
The Epicurean (1894) is Charles Ranhofer's record of what he cooked over three decades at Delmonico's in New York, and its hot-sauce chapter is essentially the French classical repertoire transcribed for an American kitchen — dozens of named derivatives, each a small variation on a mother sauce. Names like this one commemorate French nobility rather than places or techniques: sauce à la Villars is generally traced to the Duc de Villars, marshal of France under Louis XIV, in the same way that Villeroi (the entry that follows it here) recalls another marshal of the same court. Whether the eighteenth-century original bore any resemblance to Ranhofer's version is doubtful; by the nineteenth century such names had become a convention of the menu card, a way of distinguishing one cream-and-chicken sauce from the next in a kitchen that needed to keep them straight. The sieved hard-boiled yolk is the older gesture in the recipe — a thickener and enricher used long before egg-yolk-and-cream liaisons became standard, and one that survives in modern sauce gribiche and in some remoulades.