Pre-heat the oven to 200°C/400°F/Gas mark 6. Boil the potatoes whole for about 12 minutes. Meanwhile, heat the oil and fry the bay leaves and other spices for a few moments, then stir in the sugar and garlic. Add the seasoning and then mix in the yoghurt. Drain the potatoes well, prick them all over with a fork and then roll them in the yoghurt paste, making sure they are well covered. It is best to pour the paste into a large, shallow ovenproof dish to do this. Bake in the same dish for about 30 minutes, and sprinkle with the coriander leaves before serving.