Preparation and Cooking: Adjust oven rack to high position and heat the broiler. Peel and halve the onion and broil until charred; set aside. Remove fat from chicken parts and beef ribs. Put them and veal bones in a 6-quart soup kettle with salt and 4 quarts of cold water. Slowly bring to a boil. Halve the celery and carrots, quarter the celery root; add them to the soup kettle along with the remaining ingredients and simmer for 3 1/2 to 4 hours, skimming frequently until stock reduces to 2 quarts. Strain broth, discarding solids. (Can cool, cover, and refrigerate for up to 4 days or freeze for up to 1 month.)
