Minestrone Soup

Ingredients

• 3 tablespoons olive oil
• 2 large onions, coarsely chopped
• 4 carrots, coarsely chopped
• 4 celery ribs, coarsely chopped
• 3 zucchini, thinly sliced
• 6 red potatoes, peeled and cubed
• 3 quarts beef broth
• 1 (28 ounce) can plum tomatoes with liquid, chopped
• 2 (16 ounce) cans white beans, rinsed and drained
• 2 cups green beans, cut into 1-inch pieces
• 1 teaspoon salt
• 13 cup freshly grated parmesan cheese (optional)