White barley soup

Soak a cupful of barley for several hours in enough water to cover it; then boil in a quart of veal stock until tender and clear. Season with a teaspoonful of onion juice, a tablespoonful of minced parsley, and with celery salt and white pepper to taste. Thicken a pint of scalding milk with a white roux, pour the hot soup slowly upon this and serve.