Preheat oven to 375°F (190°C) and grease a baking dish.
Arrange half of the sliced potatoes evenly in the baking dish.
In a bowl mix sour cream, milk, melted butter, French onion soup mix, pepper, and salt.
Spread half of the sauce over the potatoes.
Sprinkle half of the shredded cheese over the layer.
Add the remaining potatoes and top with the rest of the sauce.
Sprinkle remaining cheese evenly on top.
Cover with foil and bake for 30 minutes.
Remove foil and bake another 15 minutes until golden and bubbly.