Instructions

1. Make the broth: In a large pot, add the chicken, onion, salt, and peppercorns. Add enough water just to cover the chicken, about 10 cups. Bring to a boil, then reduce to a low simmer. Cook, skimming occasionally, until the chicken is cooked through and the stock is flavorful, 1 1⁄2 hours. Remove chicken and save for another use. Strain the broth through a fine-mesh strainer and reserve (you should have about 8 cups). Stock can be prepared and chilled up to 3 days ahead.
2. Meanwhile, begin the tortellini: In a large bowl, combine the flour and salt. Form a well in the center and add the oil, eggs, and yolks. Using a fork, stir the eggs and yolks into the flour mixture, starting with smaller circles and growing the circles wider. Continue mixing until a shaggy dough forms.
3. Turn out the dough onto a clean work surface; knead until a smooth and elastic ball forms, about 5 minutes. Wrap tightly in plastic wrap and chill for at least 30 minutes or up to overnight.
4. Meanwhile, make the filling: In a medium bowl, stir the ricotta, Grana Padano, and a generous pinch each salt and pepper.
5. Remove the dough from the plastic wrap and cut off a 1-inch-thick slice (about one-fifth of the total); place the remainder back in the plastic wrap. Using a pasta machine set to its widest setting, roll out the dough into a long, 3- to 4-inch-thick strip. Continue passing the dough through the machine, tightening the setting each time, until it's on the seventh setting (the third finest) and the dough is thin but still opaque.
6. Lay out the rolled dough on a clean work surface and set a small bowl of water nearby. Using a round cookie or biscuit cutter, cut the dough strip into 2-inch rounds (you should get about 12 rounds per piece of dough). Keep the rounds under a damp paper towel while you work. Working one round at a time, place a scant 1⁄4 teaspoon of the filling at the center. Add a small piece of prosciutto, then wet one half of the perimeter of the dough round lightly with water. Fold the ends over the filling to meet and form a half-moon; press firmly to seal. Lightly wet one of the corners of the half-moon, then fold the two corners together to meet and form a ring. If desired, fold the top curved edge of each tortellino down over the ricotta-filled bump. Set on a lightly floured baking sheet and cover with a damp paper towel. Repeat with the remaining rounds and pieces of dough.
7. Stir the tomato sauce into the broth and bring the broth back up to heat. Meanwhile, in a medium pot of boiling, salted water, add the tortellini. Let cook until the pasta floats to the top and tastes tender, 4-5 minutes. Remove using a slotted spoon and transfer to 4 individual soup bowls. Ladle the broth into the bowls and sprinkle each with a pinch of salt. Serve immediately.