Peel and chop the onions as finely as possible. Peel and thinly dice the carrot and the celery.
Heat the olive oil in a large pot, add the whole piece of meat and brown it for a few minutes on each side to seal. Remove meat and add the onions. Brown for about 3 minutes - be careful not to burn them. Add the carrot, the celery and the marjoram, stir and cook a few minutes.
Return the meat back to the pan and add the prosciutto. Season them with a few pinches of salt and pepper. Completely cover with water, lid, and cook over medium heat for at least 2 hours (add water if necessary). The onions will become creamy and the meat tender.
Remove the meat: you can slice it and serve it as the second course of the meal.
Cook pasta according to package directions and season it with the Genovese sauce. If you opted for ziti, break them in two or three before cooking them: they are far easier to eat.
Serve the pasta hot and let each one add as much freshly grated parmesan as they like.