Radicchio, Prosciutto and Penne

1 small head of radicchio, washed and cut fine
2 ounces of prosciutto crudo, cut in thin strips
4 tablespoons extra virgin olive oil
1 medium onion, finely chopped
3 tablespoons freshly grated Parmigiano Reggiano
salt and freshly ground black pepper
1 pound penne rigata

Remove the outer leaves of radicchio, separate the rest of the leaves, wash, drain and cut into small pieces. Heat the olive oil in a large heavy saucepan and sauté onions till transparent. Add the prosciutto cut into thin strips and cook for a few minutes, till onions turn golden. Add the radicchio and a pinch or two of salt and cook, covered, about five minutes, till cooked through and soft. Cook the pasta, drain and add to the pan with the radicchio mixture for a minute or two. Remove from heat. Add the cheese and freshly ground pepper. Toss well and serve on preheated plates, or into a warm serving bowl. If too dry, add a tablespoon or two of the pasta cooking liquid till desired consistency is reached. Serves 4.