In a large bowl, combine the sliced Polish sausage, sauerkraut, sour cream, chopped onion, caraway seeds, and black pepper. Mix well.
Spread the mixture evenly into a greased 8x8 inch baking dish.
Arrange the thinly sliced potatoes over the sauerkraut mixture.
Dot the top of the potatoes with butter and sprinkle with shredded cheddar cheese.
Cover the baking dish with foil and bake for 30 minutes.
Remove the foil and bake for another 15 minutes, or until the potatoes are tender and the cheese is melted and bubbly.
Let stand for 5 minutes before serving.
Notes
This casserole can be made ahead of time and reheated. For an extra layer of flavor, consider adding a pinch of paprika or a dash of Dijon mustard to the filling.