Melt butter or margarine in saucepan. Blend in flour, 1 tsp salt, pepper and paprika. Gradually add milk and cook on a medium heat until thickened. Combine 1 tsp salt, onions, potaotes and water in saucepan. Turn to a high heat until steaming, then to a lower heat and cook for 10 minutes. Drain. Arrange 1/3 of potato-onion mixture in greased 1-1/2 quart casserole. Sprinkle with 1/3 of parsley and pour 1/3 of sauce over potatoes and onions. Repeat two more times. Bake, uncovered, at 325 degrees F. for 45 to 60 minutes or until tender and brown. Makes 6 servings.