Put one pint of milk or cream into a double boiler; add to it one pint of white stock, and a white roux made of one tablespoonful of butter and one tablespoonful of flour cooked together, but not browned. Dilute the roux to smoothness with a little of the cold milk before adding it to the soup. Let it come to the boiling-point. Season to taste, and strain into the tureen; then add one tablespoonful or more of chicken breast, veal, or celery (cut into small dice), or rice. If desired, two or more of these may be used, and the yolk of a hard-boiled egg, pressed through a sieve, sprinkled over the top. This quantity gives but one quart of soup; enough to serve to four people.