Put the freshly sliced celery root immediately into the stock which should be flavored with 1 tablespoon each oil and vinegar, 1/2 teaspoon salt, the sugar, and the chopped onion. Cook for about 20 minutes - until the celery root is quite tender and the liquid has almost boiled away. Season the celery root and beef stock with the remaining oil and a dash or two of wine vinegar, as well as with salt if you wish.
Note: If the salad is to be served as an appetizer, mix in some coarsely chopped walnut and garnish with a few walnut halves.
Nowadays, in this age of crudities, it may be more usual to substitute grated uncooked celery root, marinated in oil and vinegar, and possibly mixed with grated raw carrot.
Makes 2 - 3 cups.
From: THE CUISINES OF GERMANY by Horst Scharfenberg