2 tbsp. chopped onions
1/4 c. butter
1/4 c. flour
1 tsp. salt
1/2 tsp. dry mustard
2 c. (8 oz.) shredded Cheddar cheese
1/2 lb. ham, cut into 1/8 inch slices
6 c. cooked potato slices
Dash of pepper
1 1/2 c. milk

Saute onions in butter. Blend in flour and seasonings. Gradually add milk; cook, stirring constantly until thickened. Add 1 1/2 cups cheese; stir until melted. Toss potatoes in cheese sauce.