Passatelli in Brodo

• MAKE-AHEAD

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

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.