Distribute the potato, onion slices evenly in a large shallow casserole dish. Add a tablespoon of water and microwave, covered,for about 10 minutes. Dot with butter while still hot, sprinkle with a little salt and black pepper, then drizzle the cream slowly over the potatoes - try to coat them all fairly evenly. Sprinkle with the chives/shallots and cookin the oven at 350° for about 20 minutes, or until the top is a little browned and crusty.

Variations:
a) Replace 1 of the potatoes with 1 or 2 thinly sliced carrots
b) Sprinkle the top with some grated cheese before baking in the oven