Meanwhile, heat the oil in a heavy medium saucepan over medium heat. Add the onion, and sauté until tender about 5 minutes. Add the orzo and sauté 3 minutes. Add the hot broth, and sprinkle with salt and pepper. Bring to a boil, stirring constantly. Reduce the heat and simmer 14 minutes, stirring frequently. Add the sliced endive and continue simmering until the liquid is absorbed and the mixture is creamy, stirring frequently, about 4 minutes longer. Mix in the prosciutto and cheese. Season to taste with salt and pepper and serve right away.