Put half a pound of butter in a saucepan on the fire, and when it begins to heat, dredge in ten ounces of small pearl barley, well freed of all dust and impurities; let cook for a few minutes, then moisten with three quarts of white broth, and stir continually until it comes to a boil; salt, and cook for two hours and a half, till the barley be thoroughly done; adding three-quarters of a pound of celery roots cut in quarter inch squares, and blanched in boiling salted water for ten minutes. After the celery is well cooked; and just when serving the soup, taste it to see whether the seasoning be correct, then add a thickening of egg-yolks, cream and tine butter (No. 175).