Scalloped Tuna And Potato Casserole

Directions

1. 1
   Cook potatoes, sliced, until soft in salt water.
2. 2
   Melt butter in top of double boiler over direct heat; stir in flour and mustard.
3. 3
   Add milk, salt and pepper.
4. 4
   Stir over boiling water until smooth and thick.
5. 5
   Arrange potatoes, tuna and onion in alternate layers in greased 2-quart casserole.
6. 6
   Pour sauce over all.
7. 7
   Bake at 350° for 45 minutes.