The similar French 'Vichyssoise' Soup is always fully creamed, often served cold, and appears to be developed from an American receipt first published in the The Pittsburgh Press of Sept 17, 1905 and popularised at the at the Ritz-Carlton in New York City.
Original Receipt in 'The Book of Household Management', 1861, edited by Isabella Beeton (See Mrs.B)POTATO SOUP.
(Very Economical.)
147. INGREDIENTS: 4 middle-sized potatoes well pared, a thick slice of bread, 6 leeks peeled and cut into thin slices as far as the white extends upwards from the roots, a teacupful of rice, a teaspoonful of salt, and half that of pepper, and 2 quarts of water.
Mode: The water must be completely boiling before anything is put into it; then add the whole of the ingredients at once, with the exception of the rice, the salt, and the pepper. Cover, and let these come to a brisk boil; put in the others, and let the whole boil slowly for an hour, or till all the ingredients are thoroughly done, and their several juices extracted and mixed.
Time: 2-½ hours.
Average cost: 3d. per quart.
Sufficient: for 8 persons.
Seasonable: in winter.