Chilled Herb Soup

Ingredients

• 1 1/4 pounds sweet onions such as Vidalia
• chopped (about 4 cups)
• 1/2 stick (1/4 cup) unsalted butter
• 1/4 cup all-purpose flour
• 4 cups chicken broth
• 2 cups water
• 3 cups loosely packed fresh flat-leafed parsley leaves
• washed well and spun dry
• 1 cup chopped fresh chives (about 3 bunches)
• 6 tablespoons loosely packed fresh tarragon leaves
• 3 tablespoons fresh thyme leaves (preferably lemon thyme)
• 3/4 cup sour cream
• 1 1/2 tablespoons fresh lemon juice
• Garnish: sour cream
• finely chopped fresh chives
• and fresh thyme sprigs

Instructions

1. In a 4- to 5-quart saucepan cook onions in butter with salt and pepper to taste over moderately low heat, stirring, until softened.
2. Add flour and cook, stirring, 3 minutes.
3. Stir in broth and water and simmer, stirring, 2 minutes, or until slightly thickened.
4. Add herbs and simmer 1 minute.
5. Remove pan from heat and let mixture cool slightly.
6. In a blender puree mixture in small batches until very smooth, forcing as pureed through a fine sieve into a bowl.
7. Whisk in sour cream and salt and pepper to taste.
8. Chill soup, covered, until very cold, at least 4 hours and up to 24.
9. Just before serving, stir in lemon juice and season with salt and pepper.
10. Garnish soup with sour cream and herbs.