Lettuce and Tarragon Soup

• FAST
• MAKE-AHEAD

Ingredients

1. 4 tablespoons unsalted butter
2. 2 medium leeks (about 1 pound), white and tender green parts only, halved lengthwise and thinly sliced crosswise
3. 1 garlic clove, finely chopped
4. 4 cups chicken or vegetable stock or canned low-sodium broth
5. Salt
6. 1 head romaine lettuce (1 1/2 pounds), cored and cut crosswise 1 inch thick
7. 1/4 cup packed tarragon leaves
8. Freshly ground pepper

1. Melt the butter in a medium sauce-pan. Add the leeks and garlic and cook over moderate heat, stirring often, until lightly browned, about 10 minutes. Add the stock; season with salt. Cover and simmer over low heat for 15 minutes.
2. Stir in the lettuce and cook over moderate heat for 5 minutes. Stir in the tarragon. Puree half of the soup at a time in a blender until smooth. Transfer to a medium saucepan and gently reheat. Season the soup with salt and pepper and serve in warmed bowls.