Meanwhile, in a large skillet over low heat, cook reserved chicken fat, stirring from time to time until melted and begins to brown...about 30 minutes.
Strain fat, and reserve the melted "fat". Discard the solids.
Measure melted fat. I barely had enough so I added enough vegetable oil to equal ⅓ cup. Place in a small pot.
Add ¼ cup seltzer water (or club soda) to the pot with the fat and place over medium heat.
Add 2 bouillon cubes and cook until dissolved, mashing as it softens about 1-2 minutes. Cool for 5 minutes.
Meanwhile in a medium bowl, combine eggs, salt, black pepper, the ¼ cup of remaining seltzer water(or club soda) and the fat.
Add the cooled seltzer mixture and matzo meal, stir thoroughly (be careful not to overdo it...you don't want them heavy and dense!) Cover and refrigerate for at least 30 minutes.
Fill a large skillet with water, mid way up. Add the remaining bouillon cubes. Bring to a boil over high heat. As soon as it comes to a boil, reduce heat to medium.
Keeping hands moistened with water, shape matzo mixture into tablespoon size balls (they'll puff and fluff to a larger size as they cook).
Gently lower them all into the simmering bouillon water mixture.
Cover and simmer for 20-25 minutes until matzo balls are cooked through, and enlarged.
Using a slotted spoon, transfer matzo balls carefully to the soup pot.
Let stand for 10-15 minutes, allowing matzo balls to absorb the soup's flavors.
If made ahead, reheat covered. Serve while hot.