1. In a large saucepan, heat oil over medium heat. Add onion and cook, stirring occasionally, until softened, about 3 minutes. Add zucchini and salt, stirring to coat zucchini with oil and onion. Reduce heat to medium-low, cover, and cook, stirring occasionally, until zucchini is tender and has released juices, about 20 minutes.
2. Add black pepper, red pepper flakes, cumin, and curry; increase heat to medium-high and cook until fragrant, about 1 minute. Add broth and cook to blend flavors, about 1 minute.
3. Working in batches, fill blender jar halfway with a portion of zucchini mixture and purie, holding lid in place with folded dishtowel. Pour into large, non reactive bowl (preferably stainless steel). Add buttermilk and stir to blend. Let cool briefly to room temperature, about 20 minutes, then cover with plastic wrap and refrigerate until soup is cold and flavors have combined, at least 4 hours.
4. Stir soup to blend, and correct seasoning with additional salt and pepper if desired. Ladle into chilled bowls, garnish with minced cilantro or parsley and sweet potato chips, if using, and serve.
Source: Hannaford fresh Magazine, July - August 2007