Ingredients

1. One 4-pound chicken
2. 3 quarts water
3. 1 quart low-sodium chicken broth
4. 1 onion, halved
5. 1 carrot, halved
6. 1 celery rib, halved
7. 1 bay leaf
8. 1 teaspoon whole black peppercorns
9. One 4-ounce Parmigiano- Reggiano rind
10. Kosher salt
11. 2 ounces mortadella, cut into 1/2-inch pieces
12. 4 large eggs
13. 1 large egg yolk
14. 1 teaspoon finely grated lemon zest
15. Pinch of freshly grated nutmeg
16. 1 1/4 cups plain dry bread crumbs
17. 1/4 cup freshly grated Parmigiano-Reggiano, plus more for serving
18. 2 tablespoons unsalted butter, cut into 6 pats

Directions

1. In a large soup pot, combine the chicken, water, broth, onion, carrot, celery, bay leaf and peppercorns and bring to a boil. Simmer over low heat for 2 hours. Add the cheese rind and simmer for 1 hour. Strain the broth and discard the solids. Skim off as much fat as possible and season the broth with salt. You should have 10 cups.
2. Meanwhile, in a mini food processor, pulse the mortadella until finely chopped. Add the eggs, egg yolk, lemon zest and nutmeg and process to a loose paste. Transfer the mixture to a medium bowl and stir in the bread crumbs, the 1/4 cup of grated cheese and 1/2 tablespoon of kosher salt; the dough will be stiff. Knead the dough with your hands until the ingredients are evenly combined.
3. In a large saucepan, bring 4 cups of the broth to a gentle boil. Working in 3 batches, transfer 1/2 cup of the dough at a time to a potato ricer with large 1/4-inch holes. Squeeze 2-inch lengths of the dough into the simmering broth, cutting the dumplings with a paring knife. Repeat immediately with another 1/2 cup of dough. Stir and cook gently just until the passatelli float to the surface and are tender, about 2 minutes. Using a skimmer, transfer the passatelli to a large bowl. Repeat with the remaining dough. Save the broth in the saucepan for another use.
4. Bring the remaining 6 cups of broth to a simmer. Spoon the passatelli into 6 bowls and top with the pats of butter. Pour the hot broth on top and serve right away, passing grated cheese at the table.

Make Ahead

The dough can be refrigerated overnight. Bring to room temperature before using. The broth can be refrigerated for 5 days or frozen for 2 months.