In a covered soup pot, saute the onions and garlic in the oil on low heat for about 5 minutes, until softened. Add the ginger, turmeric, coriander, thyme, and allspice and saute for another minute, stirring to prevent sticking.
Stir in the water or stock, add the sweet potatoes, and bring to a boil. Simmer for 5 minutes, then stir in the callaloo or kale. (If you are using spinach, do not add it yet.) Add the okra and simmer for another 5 minutes. Stir in the tomatoes, lime juice, salt and spinach, if you are using it, and cook for another 3 or 4 minutes, until all of the vegetables are tender. Add more salt or lime juice to taste and stir in the coconut milk, if you like.