Classic Minestrone

INGREDIENTS

• 2 tablespoons olive oil, plus more for serving (optional)
• 1 medium red onion, chopped
• 2 medium carrots, peeled and diced
• 1 large celery stalk, diced
• 1/4 teaspoon red-pepper flakes
• 1 teaspoon minced fresh rosemary, or 1/4 teaspoon dried
• Coarse salt and ground pepper
• 1 can (14.5 ounces) whole peeled tomatoes, drained and finely chopped
• 1 large potato, peeled and diced
• 1/4 head Savoy or green cabbage (1/2 pound), cored and thinly sliced
• 1 can (15 ounces) cannellini beans, rinsed and drained
• 1/2 pound green beans, trimmed and cut into 1-inch pieces
• 1 garlic clove, minced (optional)
• 1/4 cup thinly sliced fresh basil, plus torn leaves for serving (optional)
• 3/4 cup grated Parmesan, for serving