Scalloped Potatoes

3 lbs. potatoes, peeled and thinly sliced
3 tsp. salt
3 T. butter
1/8 tsp. pepper
4 onions, thinly sliced
1/8 tsp. paprika
2½ cups milk
2 T. flour

Preheat oven to 350 degrees. Place potatoes, onions, and 2 tsp. salt in a large saucepan. Cover with water. Boil 5 minutes or until potatoes are tender. Drain. Grease an 8 x 10 x 2 pan. Put potato, onion mixture in pan. Melt butter in a saucepan. Remove from heat. Add flour, 1 tsp. salt, paprika, and pepper. Stir until smooth. Add milk. Gently boil three minutes. Pour sauce over potatoes. Bake at 350 degrees for 30 to 40 minutes. When about done, place cheese strips or slices on top of potatoes. Heat until melted. Serve hot.