Step 1

Whisk eggs in a medium bowl until no streaks remain. Add schmaltz, broth, dill, salt, and pepper and whisk vigorously to combine. Add matzo meal and whisk until incorported. Cover and chill dough at least 35 minutes (this is essential as it gives the matzo meal time to hydrate).

Step 2

Do ahead: Dough can be made 2 days ahead. Keep chilled.

Step 3

While the matzo dough is chilling, place a rack in top third of oven; preheat to 450°. Place chicken legs on a rimmed baking sheet or a large plate and sprinkle with 1½ tsp. salt; let sit at room temperature until ready to use. Spread chicken wings out on another rimmed baking sheet and roast until golden brown, 45–55 minutes.

Step 4

Transfer wings and any accumulated juices on baking sheet to a large pot. Add onions, celery, parsnip, chopped carrot, parsley, peppercorns, and 4 quarts water. Bring to a simmer and cook, adjusting heat as needed to maintain simmer, until stock is slightly reduced, 40–50 minutes. Add chicken legs and simmer until legs are very tender, another 40–50 minutes.

Step 5

While the chicken legs cook, bring 3 qt. water to a boil in a medium pot. Add 3 Tbsp. salt. Using damp hands, divide matzo mixture into 16 pieces and roll each into about 1½”-diameter ball. It’s okay to really work the dough into balls; it won’t get dense—trust us, we tried! Using a slotted spoon, carefully lower matzo balls into pot. Reduce heat to low, cover pot, and simmer gently, checking occasionally and adjusting heat if boiling too rapidly, until balls are puffed and light in color, 30–40 minutes. Don’t remove them sooner than this; they will be dense in the middle if undercooked. Remove from heat and let sit while you finish the soup.

Step 6

Transfer chicken legs to a plate and let sit until cool enough to handle.

Step 7

Meanwhile, strain stock through a fine-mesh sieve into a medium pot; discard solids.

Step 8

Remove meat from legs; discard skin and bones. Tear meat into bite-size pieces and return to stock. Add remaining thinly sliced carrots. Return stock to a simmer and cook until carrots are just tender, about 4 minutes. Taste and season soup with more salt if needed.

Step 9

Using a slotted spoon, place 2 matzo balls in each bowl. Ladle soup over. Garnish with chopped dill and a few grinds of pepper.

Step 10

Do ahead: Matzo balls can be boiled 2 days ahead. Transfer to an airtight container along with 2–3 Tbsp. cooking liquid and chill. To reheat, gently lower balls into soup and cook over medium-low until heated through, about 10 minutes.