POTATOES AU GRATIN

From 1912:

Pare and slice the potatoes rather thin and put in layers into a buttered bake dish, sprinkling each layer with salt, pepper, and bits of butter.
Pour into the dish a cupful of hot water and cover closely. Bake for halt an hour and pour in a cupful of hot milk into which you have stirred a dessertspoonful of butter. Strew fine bread crumbs thickly over the top. Salt and pepper and dot with butter. Set back in the oven and brown slightly.
Some cooks strew Parmesan cheese with the crumbs and over each layer of sliced potato. This is a matter of taste.