Prepare the pasta: On a flat work surface, mound the flour. Make a well in the center, and add the eggs and a pinch of salt. Using a fork, work the eggs into the flour until a dough forms. Form the mixture into a ball, and knead for 10 minutes, adding more flour if necessary. Wrap in plastic, and set aside for 30 minutes.

In a large skillet over medium heat, warm the butter. Add the pork loin and turkey breast, and sauté until cooked through, about 10 minutes. Place the pork, turkey, prosciutto and mortadella in a food processor, and process until well-mixed but still slightly grainy. Place in a bowl, and add the eggs, Parmigiano and a pinch of nutmeg. Season with salt and pepper to taste, mix well by hand, and set aside. (The filling can be made a day ahead, covered well and kept in the refrigerator.)

Using a pasta machine, roll out the dough until you reach the second-thinnest setting. Cut the pasta sheets into 1½-inch squares. Place ½ teaspoon of filling in the center of each square. Brush the edges of the square with water, then fold opposite corners over to form a triangle. Press to seal the edges, then bring the opposite corners together, and pinch to form tortellini. As you make them, arrange them on a floured surface so they don't stick together.

In a large pot, bring the stock to a boil. Season the stock with salt and pepper, add the tortellini and cook until done, about 2 minutes. Ladle the tortellini and some stock into soup bowls, and sprinkle with Parmigiano-Reggiano.