Heat oven to 325?F. Place potato slices in a bowl. Mix together flour, mustard, salt, pepper and paprika, onion and half the cheese. Sprinkle over potatoes and mix together with a tossing motion. Turn potatoes into a deep 1 1/2 quart casserole. Pour in milk or cream. Sprinkle with cheese. Cover and bake 1 hour. Uncover and bake about 30 minutes longer or until potatoes are fork tender.