Lightly sauté the onions in a pot. Add chopped snake gourd and a little water and allow it to cook. When it is partially cooked (make sure that it does not overcook, the green color should remain), add the celery and allow it to cook a little longer. Both vegetables should remain green. Add some vegetable stock and process in a blender. Once the soup is a creamy paste, add water and salt, as needed. This soup tastes good served hot or cold.