Crema de Calabacitas (Cream of Zucchini Soup)

3-4 medium or 2 large zucchini (1 lb.)
2 c water
salt
2 T chopped parsley
2 T butter
2 T minced onion
1 T flour
1 13-oz. can evaporated milk
1 cup chicken broth

Wash zucchini. Cut off stem ends, then cut in large pieces. Place in a large saucepan. Add water and a pinch of salt; bring to a boil. Cover and cook until tender, about 20 minutes. Cool zucchini in cooking liquid. Place zucchini, 1 c liquid, and 2 T parsley in blender. Process until pureed. Heat butter in a medium saucepan. Add onion; cook until tender but not browned. Stir in flour. Cook and stir 1 minutes. Add pureed zucchini mixture, evaporated milk, and chicken broth. Stir to blend. Season with salt if needed. Stir over medium heat until soup comes to a boil. Serve at once or chill and serve cold. Serves 4-6