Mornay-style Potato Gratin
Peel the potatoes and place in a bowl of cold water.
Drain the potatoes in a colander.
Drizzle the sauce into the bottom of a deep casserole. There is no need to create a thick uniform layer, as the sauce will spread out during cooking.
Cover the sauce with a layer of overlapping potato slices.
Drizzle more sauce over the potatoes. You do not need a full layer of sauce to completely cover the potatoes. If you do, your final dish will be too liquid. You really want just enough sauce so that the weight of the potatoe above will cause it to spread out into a very thin layer. The potatoes should end up bound together by the sauce, not swimming in it. Repeat the process until the potatoes are all used up. Depending on the shape of your backing dish, you should get 5-10 layers of potatoes.