In a large bowl, whisk together eggs, schmaltz and seltzer.
Then add matzo meal, onions, baking powder, salt and pepper. Mix just until combined. Do not overmix.
The mixture will be sticky, so refrigerate dough for 30 minutes or up to 4 hours so it is not as sticky.
Bring a large pot of salted water to a boil, and then reduce to a simmer.
Shape the matzo mixture into 25 or so 1-inch balls, and place in the water. Cover and simmer for 30-40 minutes until puffed up and cooked through.
Heat up your broth separately and then, add carrots, parsnips, celery and any other veggies you choose and chicken, and simmer covered for an 10 minutes until the veggies are tender. Serve with balls!
Add salt to taste and garnish with parsley or dill.