Preheat oven or roaster to 350.

30 pounds potatoes
3 quarts white sauce
4 pounds shredded cheese
10 pounds cubed ham
OPTIONAL 2-3 pounds onions, chopped or thin sliced
salt and pepper to taste

Layer every thing in, pour the sauce over, stirring a bit to get it down to the bottom.

Grease the roaster cook pan and either dust with grated Parmesan cheese or line it with foil or parchment paper to minimize cleanup.

Cooking time; if the potatoes are raw and the sauce is not hot (not just made), they take 2 to 2 1/2 hours. If you parboil the potato slices about 10 minutes and the sauce is just made, they take about an hour to 70 minutes.

In the oven, cover the first 30 minutes, then uncover.