Instructions:

Au Gratin Potatoes

About 4 large Idaho potatoes, peeled,
    sliced very thin
1 or 2 onions, sliced thin

Layer the above in a buttered dish. Sprinkle salt and fresh ground black pepper between the layers

Sauce
4 tablespoons (1/2 stick) butter
1 to 2 tablespoons flour
About 2 cup milk
3/4 to 1 cup cheese (more or less) sharp
    Cheddar, Velveeta, Swiss, etc., grated
Bread crumbs, plain or mixed with  parmesan cheese

Melt butter, add flour to make a loose paste ( you have to judge this one...the thicker the paste, the thicker the sauce). Don't let it brown. Add milk and mix together with a whisk until it gets thick. Add some salt and pepper. Add cheese. Pour sauce between the layers. You can add more cheese between the layers too. Top with cheese and a thin layer of plain bread crumbs. Bake in a 400 degree F oven for 1 1/2 hours.