I make a blond roux with butter, add enough whole milk to make a thin sauce, which I season with salt and white pepper. I then parboil waxy potatoes, peel and slice thinly, layer them in a glass or porcelain baking dish, spooning the sauce between the layers. This is baked in a medium-high oven (350 or so) until the potatoes are tender through and the top somewhat browned.
