- 1/2 cup olive oil
- 1/2 large onion, chopped (about 1 cup)
- 1 large stalk celery, chopped (about 1/2 cup)
- 1 large carrot, chopped (about 1/2 cup)
- 1 small leek, white and pale green parts only, washed and chopped (about 1/2 cup)
- 1 large russet potato, peeled and diced (about 1 cup)
- 1/2 cup loosely packed fresh flat-leaf parsley, coarsely chopped
- 1/2 cup fava beans (freshly shelled, or soaked if dry)
- 1 cup canned crushed plum tomatoes, with their juices
- 1 medium zucchini, trimmed and chopped (about 1 1/2 cups)
- 1/2 cup fresh green beans, cut into 1-inch-long pieces
- 1/2 cup shelled fresh or frozen peas
- 1 cup loosely packed chopped fresh spinach (or any fresh greens with stems removed if necessary)
- One roughly 2-inch-square Parmigiano-Reggiano rind, rinsed
- Salt and freshly ground black pepper
- 1/4 cup pesto
- In a medium saucepan over moderate heat, warm the oil. Add the onion, celery, carrot, leek, potato, and parsley, and sauté, stirring frequently, until the vegetables are soft, about 5 minutes.
- Add the fava beans, tomatoes, zucchini, and 2 quarts of water to the pot. Bring the soup to a boil, then add the green beans, peas, spinach, and the Parmigiano-Reggiano rind. Reduce the heat to moderately low, season to taste with salt and pepper, and simmer until the beans and potatoes are fully cooked and tender, about 20 minutes.
- Remove and discard the Parmigiano-Reggiano rind. Divide the soup among heated soup bowls and top with the pesto. Note: You may cool, cover, and refrigerate the soup up to 3 days or freeze it for up to 2 months.