Zucchini And Watercress Soup
["4 Tbsp. butter", "2 c. chopped onion", "3 c. chicken broth", "2 lb. zucchini (4)", "1 bunch watercress", "salt/pepper to taste", "fresh lemon juice", "* 1 c. heavy cream (optional)"]
["Melt butter in large pot; saute onions.", "Lower heat; cover. Stir occasionally until tender and lightly cover, 25 minutes.", "Add broth.", "Chop zucchini (trim ends).", "Drop in broth.", "Return to boil. Reduce heat until tender, 20 minutes.", "Pull leaves and smaller stems off watercress.", "Rinse well.", "Remove soup from heat.", "Add watercress.", "Cover and let stand 5 minutes.", "Pour soup through strainer; reserve liquid.", "Put solids in food processor.", "Add 1 cup of liquid.", "Process until smooth.", "Return to pot and add about 2 more cups of liquid and/or* 1 cup cream and 1 cup liquid.", "Season. Simmer to heat through."]
["butter", "onion", "chicken broth", "zucchini", "watercress", "salt", "lemon juice", "heavy cream"]