Slice 3 pounds of Yukon Gold potatoes ¼ inch and simmer them for about 8 minutes or until they are tender. Whisk ¼ C flour into 3 Cups low-fat milk (2%) over low heat.
While the potatoes are simmering away, bring the milk to a slow boil, stir a lot and believe it or not, it gets nice and thick….Add lots of black pepper, salt to taste and ¼ t mace. Also add 1 C of grated Gruyere cheese.
Arrange about ½ of the potatoes in a greased 9 X 13 casserole; pour over ½ of the sauce. Make another layer of potatoes and sauce.