Soak the sultanas in milk. Meanwhile boil the potatoes until tender. Drain, cool briefly then peel and mash with salt, pepper and half the butter.
Grease a gratin dish with the remaining butter and spread 1/3 of the potato over the bottom. Add the chutney, half the cheese, half the remaining potato then the prawns. Cover with the remaining cheese and top with potato.
Fry the breadcrumbs in a little extra butter then mix in the curry powder, sultanas and parsley. Make a well in the centre of the dish and pour in the spicy crumbs.
Bake in a preheated oven 190 C, Gas 5 for 20 minutes.