Butter a deep baking dish. Peel and thinly slice three medium potatoes and two onions. In bottom of dish, put half the potatoes and onions. Salt and pepper and dot generously with butter. Cover with a thick layer of fish fillet (or flaked, canned salmon). Season and again butter generously. Layer with remainder of potatoes and onions and season again. Pour in enough milk to reach top layer. Sprinkle with paprika and bake one hour at