Heat the oil in a large pot over medium heat. Sauté onion until just softened. Add in sausage and garlic and continue to cook for 2 minutes. Add in rosemary, bay, salt and pepper, and spinach. Sauté for 5 minutes or until spinach is wilted. Stir in beans and broth. Bring to a boil, reduce heat and simmer for 10 minutes. Remove the bay leaf. Ladle the soup into bowls and top with grated Parmesan. Serve alongside a salad and some crusty bread. Serves 4 to 6