Let the peas or beans soak over night in three quarts of cold water. Put the soaked peas or beans into a saucepan with two quarts of water and a ham-bone, if you have it, otherwise it may be omitted. Let simmer for four or five hours, or until the peas or beans are perfectly soft. (Add more water from time to time, if necessary.) Then pass them through a sieve; add to the pulp enough stock, or milk, or water to make a soup of the consistency of cream. Put it again into a saucepan on the fire; season, and add a roux made of one tablespoonful of butter and one tablespoonful of flour cooked together; dilute the roux to smoothness with a little of the soup before adding it to the pot.
The roux will hold the particles of peas or beans in suspension. Without it they are liable to precipitate.
An onion may be boiled with the peas or beans if desired.
Serve croutons on the soup, or pass them.