Bring a large pot of water to a boil.
In the meantime, heat the oil in a frying pan. Once hot, add the beef and pork and cook until fully browned and well cooked through (cooking time will vary depending on the size of the meat pieces).
While the meat is cooking, boil the Swiss chard in the previously prepared pot of water for about 20 minutes, until tender.
At the same time, soak the bread in broth until soft.
Once the meat and Swiss chard are ready, place the beef, pork, Swiss chard, cheese, soaked bread, mortadella, nutmeg, and pepolino (wild thyme) into a meat grinder or food processor. Blend until finely minced and well combined.
Season with salt and black pepper to taste, adjusting gradually by tasting the mixture. Then add the egg and blend again until the filling is smooth and fully incorporated.