Mix 3 eggs in a ceramic bowl. Add nutmeg and lemon zest. Beat this mixture with a wire whip. Add the cheese and the bread crumbs (see Cook's Note). Add salt to taste. Heat the broth. While boiling, strain the dough using a strainer with large holes (3/8 of an inch diameter) directly into the boiling broth and lower the flame to avoid breakage which can occur from water that is boiling very rapidly. If you wish to save any leftovers, take a flat dish and sprinkle it with some bread crumbs and a pinch of flour. Place the Passatelli on it, cover with plastic wrap and freeze immediately.
This consistency should be the same as a potato puree. If it comes out too hard, add some broth to soften it and if it comes out too soft, add some more bread crumbs.