I wish that picture were sharper.
I tend not to measure things, but just throw it together as I go.
4 cups thinly sliced peeled potatoes
3 T flour
4 T minced onion (and garlic)
2 - 2.5 cups hot milk
Spray pan with cooking spray. Arrange a layer of potatoes; sprinkle with flour, dots of butter, onion, salt and pepper. Repeat for 3 more layers, omitting the flour on the top layer. Pour hot milk over. Bake at 350° for 30 minutes covered and an additional one hour uncovered.
A great variation is to sprinkle each layer with grated cheese and/or bacon. Like this:
This is the original cookbook.