Place chicken in a large soup pot. Cover with water and bring to a boil. Lower the heat to a simmer and skim as needed. Simmer 10 minutes and add vegetables and herbs. Bring back to a boil and simmer, partially covered, for 1 1/2 hours. Strain, removing fat from surface, and reduce to 6 cups, to concentrate flavor.
In a bowl mix the eggs, seltzer, chicken fat, salt and pepper. Gradually stir in the matzoh meal until everything is well combined. Chill, covered, in the refrigerator for at least 4 hours and up to 8 hours
Bring a pot of salted water to a boil and using cool, wet hands, shape the matzoh mixture into eight balls about 1 1/2-inches in diameter. Reduce the heat to simmering and gently add the matzoh balls. Cover the pot and poach the matzoh balls in the barely simmering water for 25 minutes. Add matzoh balls to soup and serve. Drink: Seltzer