3/4 cup plain low-fat yogurt, whisked until smooth
1/4 cup fresh mint leaves, washed well, spun dry, and chopped fine
Directions
In a 31/2- to 4-quart heavy saucepan heat oil over moderately high heat until hot but not smoking and sauté one third zucchini, stirring occasionally, until golden. Add remaining zucchini and water and simmer until zucchini is very tender, about 15 minutes. Cool mixture slightly and in a blender purée in batches until smooth, transferring to a bowl. Stir in yogurt, mint, and salt and pepper to taste. Chill soup, covered, at least until cold, about 6 hours, and up to 1 day. Before serving, season with salt and pepper if necessary.