Chilled Zucchini Soup

Preparation Cook shallots in oil in a 4-quart heavy saucepan over moderate heat, stirring occasionally, until softened, about 5 minutes. Add zucchini, zest, salt, and pepper and cook, stirring occasionally, until zucchini is softened, about 5 minutes. Add broth and water and simmer until zucchini is tender, about 3 minutes. Purée zucchini mixture, including zest, along with parsley and dill in a blender (in 2 batches if necessary) until smooth (use caution when blending hot liquids). Transfer to a metal bowl, then set bowl into a larger bowl of ice and cold water (to quick-chill). Cool, stirring occasionally, about 20 minutes. Stir in buttermilk and season with salt. Cooks' note:Soup (with buttermilk or yogurt) can be made 1 day ahead and chilled, covered. (If making soup ahead, cooling in ice bath is not necessary.) Stir well before serving.

Preparation Cook shallots in oil in a 4-quart heavy saucepan over moderate heat, stirring occasionally, until softened, about 5 minutes. Add zucchini, zest, salt, and pepper and cook, stirring occasionally, until zucchini is softened, about 5 minutes. Add broth and water and simmer until zucchini is tender, about 3 minutes. Purée zucchini mixture, including zest, along with parsley and dill in a blender (in 2 batches if necessary) until smooth (use caution when blending hot liquids). Transfer to a metal bowl, then set bowl into a larger bowl of ice and cold water (to quick-chill). Cool, stirring occasionally, about 20 minutes. Stir in buttermilk and season with salt. Cooks' note:Soup (with buttermilk or yogurt) can be made 1 day ahead and chilled, covered. (If making soup ahead, cooling in ice bath is not necessary.) Stir well before serving.