Cream-less Cream of Celeraic Soup

1 head celery, washed, trimmed of strings, and coarsely chopped (include some leaves)
1 celeriac, peeled and diced
3 medium onions, peeled and diced
1 quart chicken stock
3/4 teaspoons celery salt
1/2 teaspoon celery seed
Freshly ground pepper
Fresh parsley, finely chopped

Simmer the vegetables, covered, in the chicken stock in a large saucepan until tender, about 15 minutes. Drain and reserve cooking liquid. Puree vegetables, adding a little liquid as needed. Stir the puree into the reserved cooking liquid and add the seasonings. Serve hot or cold. Freezes well.