For the broth: Place the capon in plenty of water with the cleaned carrot, celery, and onion. Cook for about two hours, skimming off any foam when needed. For the filling: Sauté the minced chicken and pork in a large pan over a high flame with two tablespoons of olive oil, salt, and pepper. Stir continuously. Once cooked, chop the meat with a knife together with the prosciutto, transfer to a bowl, and mix in the pecorino and a pinch of nutmeg. For the pasta: Combine the flour and eggs, working the dough for about ten minutes, first with a fork and then by hand, until smooth and even. Leave it to rest while the broth is cooking. Roll out the dough with a rolling pin, then leave it to rest for about half an hour. Cut the pasta into rounds using a round cutter, place a small ball of filling in the centre of each, fold into a half-moon, and seal the tips together to form the traditional cappelletto shape. Cook the cappelletti in plenty of broth and serve piping hot.