Chilled Summer Squash Soup

In a large saucepan, heat olive oil over medium heat. Add green onions (or onion) and garlic and saute until just tender. Add squash and saute, about 5 minutes, to cook out some of the liquid. Then add enough water to just cover the squash. Reduce heat and simmer until squash is completely tender. Use a blender or immersion blender to puree mixture into soup. Stir in yogurt and mint and season to taste. Chill about 2 hours or keep the refrigerator for up to 2 days. Serve garnished with a little dollop of yogurt and some more chopped mint.