Preparation time: 15 minutes. Cooking time: 25 minutes. Yield: 5 cups. Melt butter in a large saucepan. Add celery, Onion and lemongrass. Cook gently until Onion is tender, 15 minutes. Add cucumbers and stock. Heat to a boil; reduce heat, cover and simmer until cucumber is tender, 10 minutes. Strain solids from liquid, reserving both. Puree solids with spinach and cilantro in a blender or food processor. Add reserved liquid, cream, salt and pepper; mix until smooth. Serve warm or chilled