How to Make It
In a large saucepan, melt the butter in the oil. Add the onion and cook over moderate heat until softened, about 3 minutes. Add the garlic and cook, stirring, until softened but not browned, about 2 minutes. Add the bacon and cook, stirring frequently, until the fat is rendered, about 5 minutes. Add the callaloo, basil, parsley and celery leaves and cook over moderately high heat, stirring occasionally, until the greens are wilted and barely tender, about 7 minutes.
Add the water to the saucepan and bring to a boil. Cover and cook over moderate heat until the greens are soft, about 10 minutes. Puree the soup in batches in a blender until perfectly smooth. Return the soup to the saucepan, add the cream and season with salt and pepper. Bring to a simmer and then serve in soup plates.