From: The Thorough Good Cook

Sauces: 26. German Sauce (Sauce Allemande)

To make this sauce, the remains of the liquor in which fowls have been boiled, or chicken consommé, or indeed anything which has a flavour of chicken, should be added to an equal quantity of smooth sauce and set to simmer till reduced; after which skim, remove the fat, add the yolks of two or three eggs, a piece of fresh butter of the size of a walnut, and pass through a sieve.