Add chicken stock to a deep pot and bring up to a simmer.
While waiting for the stock to heat, combine the ground meat with egg, breadcrumbs, cheese, nutmeg, salt and pepper in a bowl. Roll into small walnut-size balls. Once stock is simmering, add meatballs. Let the stock come back up to a simmer, then add the tortellini and cook according to package directions.
While the dumplings and tortellini are cooking, place the parsley leaves, lemon zest and garlic in a pile on your cutting board. Run your knife through it until it is finely chopped and mixed together.
To make sure the meatballs are cooked through, split one open and make sure there is no pink left in the meat. To serve, ladle some of the broth with dumplings and tortellini into a shallow bowl and top with a sprinkle of the parsley mixture and some Parmigiano Reggiano.