Cut celery and leaves into small pieces to make 4 cups solidly packed. Cover with 4 cups water and 2 teaspoons salt. Cook gently in an uncovered saucepan about 1 hour or until very tender. Put through a food mill or ricer, and press out as much of the pulp as possible. Add enough milk or cream to celery mixture to make 4 cups.

In a medium size saucepan melt 1/2 cup butter; add 1/2 cup sifted flour. Then slowly add above mixture, a little at a time, stirring constantly. Cook slowly to simmering point, season further if necessary, and cook several more minutes. Serves 4 to 6.