1 medium onion, chopped
 
3 Tbsp butter or margarine
 
3 Tbsp flour
 
1 tsp salt
 
1/4 tsp pepper
 
1/2 tsp dry mustard
 
1-1/2 cups milk
 
1-1/2 cups grated cheese
 
4 large potatoes, sliced 1/4" thick
 
2 cups diced, cooked ham
 
1/2 cup sliced celery
 
1/2 cup chopped green pepper
Saute onion in melted butter until tender.Stir in 
flour, salt, pepper & mustard. Gradually pour in 
milk, and stirring constantly, cook until sauce is 
thickened. Add cheese and stir until blended. In a 
greased 3 qt casserole, alternate layers of sliced 
raw potatoes, ham, celery, and green pepper. Pour 
over part of the cheese sauce, and continue to 
arrange ingredients in layers until all are used. 
Pour remaining cheese sauce over all. Bake, covered, 
in a 350° oven for 1 hour. Remove cover and bake 
another 30 minutes, or until potatoes are tender and 
top is lightly browned.
 Makes 6-8 servings