Remove fat from prosciutto. Cut the fat into strips and lard the veal leg by inserting them into small incisions in the meat in the direction of its fibers. Tie leg with kitchen twine.
Poke cloves into the two whole onions, so that you will be able to remove them from the pan juices before serving. Melt butter in a wide pan over medium heat, add chopped lean prosciutto and the 2 whole onions with cloves.
Sauté prosciutto until golden, then add veal and brown evenly. Add peeled carrot, cut into rounds, and a bunch of parsley tied together with some celery leaves. Splash with white wine, season with salt and pepper and cover with a lid.
Cook for 50 minutes over very low heat, turning the meat often and adding ladlefuls of warm broth, if the meat looks dry. Turn off the heat, remove vegetables, discard cloves and pass through a food mill. Slice the veal thin and serve with sauce and vegetable purée.