Peel potatoes and slice thinly. Put a layer of potato in base of greased ovenproof dish, sprinkle with salt and pepper. Peel onions, slice thinly, arrange a layer of onions over potato slices. Put cream in saucepan, stir over medium heat until cream is heated through. Spoon approximately 1/4 cup cream over onion slices. Continue in layers of potato, salt, pepper, onion and cream, finishing with a potato layer. Bake, covered, in moderate oven 30 minutes. Remove the cover, cook for a further 45 minutes or until the potatoes are tender and golden brown.