This soup is for all those home gardeners who plant zucchini and basil only to find their kitchen brimming with it come harvest.
- 2 tablespoons olive oil, plus more for garnish
- 1/2 pound shallots (about 6), halved and thinly sliced
- 1 teaspoon fresh thyme leaves, finely chopped
- 4 garlic cloves, thinly sliced
- 2 pounds zucchini (about 6), cut crosswise into 1/8-inch-thick rounds
- 2 teaspoons kosher salt
- 1/4 teaspoon freshly ground black pepper
- 4 cups low-sodium vegetable or chicken broth
- 2 cups toasted California walnut halves, plus more for garnish
- 3 cups (about 2 ounces) packed fresh basil leaves, plus more for garnish
- 1 cup low-fat plain yogurt
- 1 teaspoon freshly squeezed lemon juice
- Heat oil in a large saucepan over medium-high heat. When it shimmers, add shallots and cook, stirring occasionally, until golden brown, about 5 minutes. Add thyme and garlic and cook until fragrant.
- Stir in zucchini, salt, and pepper, reduce heat to medium, and cook, stirring occasionally, until zucchini is very soft, about 10 minutes. Add broth and simmer until zucchini is falling apart, about 20 minutes.
- Place half of the zucchini mixture and half of the walnuts in a food processor fitted with a blade and process until smooth, at least 2 minutes (use caution when blending hot liquids). Transfer to a medium bowl, then repeat with remaining soup.
- Set soup bowl into a large bowl of ice water, and set aside to cool, stirring occasionally until room temperature, about 20 to 30 minutes.
- Transfer to the refrigerator to chill thoroughly, at least 1 hour. Meanwhile, blend or puree the basil, yogurt, and lemon juice together until smooth. (Soup can be made through this step up to 3 days ahead. Store soup and yogurt mixture separate and both covered in the refrigerator.)
- Just before serving, stir in yogurt mixture, taste and adjust seasoning as desired. Serve topped with chopped walnuts, a drizzle of olive oil, and a few torn basil leaves.