
Combine all of the ingredients in a large pot. Cover and bring to a boil over high heat. Reduce to a bare simmer and cook, partially covered, for an additional 2 hours.
Whisk together the schmaltz and the eggs. Stir in the seltzer.
While the matzo balls are cooking, make the soup. Bring the skimmed stock to a boil and reduce to a simmer.
Recipe yields about 18 matzo balls or 9 substantial servings.