To make the creamy sauce, blend the condensed soup, milk, and sour cream in a bowl.
Put half of the sliced potatoes in a 9 by 13-inch baking dish that has been oiled.
Spoon half of the cooked ground beef over the potatoes.
Scoop half of the creamy sauce over the potatoes and steak.
Using the leftover steak, potatoes, and sauce, repeat the layers.
Shred cheddar cheese and, if using dry herbs, paprika over the top.
Bake for an hour, covered with aluminum foil in the preheated oven.
Once the potatoes are soft and the top is golden and bubbling, remove the cover and bake for a further 20 to 30 minutes.
To make slicing simpler, let the casserole cool for a few minutes before serving.