Au Gratin potatoes

Ham and au gratin potatoes have always been my favorite meal that grandma made.  Here is her potato recipe:

Cook 6 medium potatoes in boiling salted water until tender.  Drain, peel, cool, and dice.  Place potatoes in a 9x13 greased baking dish.  Melt ½ c butter add ½ c enriched flour.  Add 4 cups milk and cook over low heat until thick, stirring constantly.  Remove from heat. Add 1tsp salt, and 2 cups grated cheddar cheese.  Stir until cheese melts.  Pour sauce over potatoes. Sprinkle top with 2 cups grated cheddar.  Bake at 375 for 25 minutes or until golden brown.