I layer potatoes, bacon, spring onion or shallots, then pour over a mixture of cream, sour cream and a beaten egg. Then sprinkle a bit of bacon and shallots on the top, then top with cheese (either cheddar if I'm fooling myself the kids will eat it, or gruyere if its for adults.

I par boil the potatoes first so that they definitely cook and the top ones get really yummy and crispy.