Greenport Soup

4 cans (13 1/4 ounces each) chicken broth
1 package (10 ounces) frozen tiny peas.
1 head of leafy lettuce (butter lettuce)about 1/2 pound, shredded.
1/2 cup of chopped scallions
1/2 cup (packed) Italian flat-leaf parsley
4 tablespoons of unsalted butter
3 tablespoons all-purpose flour
1/4 cup dry sherry
1/2 cup sour cream
Salt and freshly ground pepper
Parmesan Croutons

1. In a large heavy saucepan, combine the chicken broth, peas, lettuce, scallions, and parsley. Reduce the heat to low and simmer for 15 minutes.
2. In a blender or food processor, puree the soup in batches until very smooth. Alternatively, an immersion blender can be used to puree the soup in saucepan.
3. In a large sauce pan, melt the butter over low heat. Add flour and cook stirring for 2 or 3 minutes without letting the roux color. Whisk in the pureed soup and the sherry. Bring to a simmer over moderate heat. Cook for 5 minutes to blend the flavors. Remove from the heat. (The recipe can be prepared to this point up to one day ahead.) Let cool, cover and refrigerate, reheat before proceeding)
4. Stir the sour cream into the hot soup. Season with salt and pepper to taste. Serve with Parmesan croutons.