Preparation Heat 3 tablespoons oil in heavy large pot over medium heat. Add onion, carrot, and celery and sauté until vegetables are soft, about 10 minutes. Add beans, broth, sage, Parmesan rinds, and prosciutto; simmer over medium-low heat, stirring occasionally, until flavors blend and soup thickens slightly, about 40 minutes. Using tongs, remove cheese rinds. Puree about 5 cups soup in processor and return to pot. Season with salt and pepper. (Soup can be made 2 days ahead. Refrigerate uncovered until cold, then cover and keep refrigerated. Rewarm before serving.) Ladle soup into bowls and serve, passing grated Parmesan cheese and additional olive oil separately.
Preparation Heat 3 tablespoons oil in heavy large pot over medium heat. Add onion, carrot, and celery and sauté until vegetables are soft, about 10 minutes. Add beans, broth, sage, Parmesan rinds, and prosciutto; simmer over medium-low heat, stirring occasionally, until flavors blend and soup thickens slightly, about 40 minutes. Using tongs, remove cheese rinds. Puree about 5 cups soup in processor and return to pot. Season with salt and pepper. (Soup can be made 2 days ahead. Refrigerate uncovered until cold, then cover and keep refrigerated. Rewarm before serving.) Ladle soup into bowls and serve, passing grated Parmesan cheese and additional olive oil separately.