In a large soup pot, melt the butter over medium heat until frothy, then saute the onion, garlic and pancetta for one minute. Before the mixture browns, add the cabbage, mix thoroughly, and let simmer over low heat for a few minutes longer. Add the broth, cover and let simmer for 15 minutes. Season to taste. Rub each slice of toast lightly with fresh garlic, place two in each soup bowl and top with a slice of Provolone cheese. Add the boiling hot broth and serve immediately.