I make mine in the microwave from scratch. I just spray my casserole dish with spam and layer my potatoes,onions,salt and pepper and add little slices of butter,sprinkle each layer with flour to thicken and then after that I add a mixture of evaporated milk and whole milk.I sometimes just add fresh chives to the top.I put a layer of waxed paper on top and cook until the potatoes are tender.I just made them yesterday. Yummy!!