Recipe - Scalloped Potato And Tuna Casserole

4 cup Potatoes; Pared & slice thin
3 tablespoon Butter
One fourth cup Flour
2 tablespoon Mustard; prepared
2 cup Milk
1 teaspoon Salt; to taste
1/8 teaspoon Pepper; to taste
1 cn Tuna; 7oz Use 2 cans for a
Dish
1 cup Onions; peel and slice thin

Cook potatoes in boiling salted water 10 minutes,;Drain. Meanwhile melt
butter in top of a double boiler over direct heat. Stir in flour, then
mustard. Add milk, salt and pepper to taste, and stir over boiling water
until smooth and thickened. Arrange the cut or sliced up potatoes,tuna and onions in
alternate layers in a greased 2 quart casserole. Pour sauce over all, and
BAKE in a moderate oven 350 degrees for 45 minutes. Makes 6