This section is from the book "The Epicurean", by Charles Ranhofer. Also available from Amazon: The Epicurean, a Complete Treatise of Analytical and Practical Studies on the Culinary Art.
I believe it to be more advisable to select fresh vegetables for making cream soups, and to thicken them with raw egg yolks, butter and cream. The flavor of the fresh vegetables combined with the velvety liaison, helps to make these thick soups highly estimated, even were the cream and eggs to be suppressed. Purees can be made of these creams, by finishing them as indicated in the puree soups. For Lenten cream soups, moisten them with a vegetable stock instead of broth, and use lean bechamel, in the place of veloute. Cream soups will be improved by passing them through a tammy.
Trim well some artichoke bottoms so that all the green part of the leaves be removed; mince up two pounds of this, blanch and drain them. Put two ounces of butter in a saucepan, and when very hot, set in the artichokes and fry them without browning; moisten with two quarts of broth; cover the saucepan, and let boil slowly until the artichokes are done, then drain and mash them in a mortar; and pass the puree through a fine sieve; put it back into a saucepan, and dilute it with its own broth, adding one pint of veloute sauce (No. 415). Set it on the lire and stir con-constantly, bearing on the bottom of the saucepan with a spatula; let boil up once, then remove all the fat; season with salt, sugar, and nutmeg, and thicken the soup with raw egg-yolks, cream and butter. The quantity of liaison for each quart of this soup, is two egg-yolks, one gill of cream, and two ounces of butter. Serve separately some Savarin croutons, a quarter of an inch square, and dried in the oven.