Adding a rind of Parmesan cheese brings a rich flavor to this meatless soup.
- 4 tablespoons extra-virgin olive oil, plus more for drizzling
- 1 onion, chopped (about 1 1/2 cups)
- 3 cloves garlic, minced
- 4 small zucchini, trimmed and quartered lengthwise, chopped into 1/2-inch pieces
- 3 celery stalks (the tender inner stalks with leaves), sliced crosswise into 1/4-inch slices
- 1 small head cauliflower, cored, florets removed and separated into bite-sized pieces
- 6 ounces green beans, sliced in 3/4-inch pieces (about 1 cup)
- 1 small head cabbage, cored, outer leaves discarded, and thinly sliced
- 16 ounces fresh or canned tomatoes, chopped (about 2 cups)
- 2 tablespoons coarse salt
- 1/2 teaspoon freshly ground black pepper, plus more for serving
- 1 rind of Parmesan cheese (optional)
- 1 1/2 cups cooked chickpeas, or 1 (15-ounce) can, rinsed and drained
- 2 large whole basil sprigs
- Freshly grated Parmesan cheese
Place 2 tablespoons of the olive oil, the onion, and garlic in a large heavy-bottomed soup pot over medium heat. Cook slowly, stirring occasionally, until the onion is translucent, about 3 minutes. Add the zucchini and the celery and keep cooking, stirring occasionally, for 2 minutes more. Add another tablespoon of the olive oil and the cauliflower and cook 5 minutes, stirring occasionally, as the vegetables slowly begin to soften. Stir in the green beans, cabbage, and remaining olive oil and cook, stirring occasionally, for another 2 minutes. Stir in the tomatoes and 2 cups water and simmer until all of the vegetables are softened, 5 to 8 minutes more.
Add the salt, pepper, and Parmesan cheese rind and stir. Add more water if needed for the desired consistency -- it should be very thick. Cover and simmer 30 minutes. Add the chickpeas and basil sprigs and cook until chickpeas are heated through, 5 to 6 minutes. Serve in bowls with the Parmesan cheese grated over top and freshly ground pepper, and drizzle with olive oil.