Warm a large, fairly shallow serving dish (ideally round), in a low oven. Wash the spinach thoroughly and remove the stems. Peel the ginger and garlic and chop together finely. Cut the chillies open lengthways under running water, discard the seeds and stems, then finely slice crossways.
Bring a little water to the boil in a large saucepan. Add the spinach, cover and cook for only a min