When Margaret Mallory was a newspaper food editor, winemakers she dined with often shared their recipes. She has added her own touches to this favorite. It's good hot or cold, and works as a starter or for lunch.
In a 3- to 4-quart pan over medium-high heat, stir oil, onion, carrots, and garlic until onion is limp, 5 to 7 minutes. Stir in white wine and bring to a boil. Pour mixture into a large bowl.
To pan, add broth and vermouth. Place over high heat, cover, and bring to a boil. Add squash. Cover and simmer over low heat until squash is tender when pierced, 10 to 12 minutes.
A portion at a time, whirl squash mixture in a blender until smooth. As purèed, add to onion mixture.
To serve hot, return soup to pan and stir over high heat until hot, 2 to 3 minutes. To serve cool, chill quickly by nesting pan in ice water; stir frequently until cold, 20 to 25 minutes. If making ahead, cover and chill up to 1 day. Add salt and pepper to taste.
This soup was pretty bland until I punched it up. I added a lot of salt and pepper, as well as some lemon juice. Then I garnished with sour cream and cayenne pepper.