Ham and Potato Casserole

7 - 8 medium potatoes
1 box (medium) Velveeta® cheese
2 cans (10-3/4 oz. each) cream of mushroom soup
2 large onions, chopped
Shredded cheddar cheese
1/2 cup milk
1 stick butter or margarine
3 lb. canned ham, diced
1 can mushrooms

      Heat oven to 375ºF (190ºC).  Peel and slice potatoes and place in salted water on top of stove for 10 minutes.  After potatoes have reached a boil, place cheese, 1/2 stick butter, onions, mushrooms and mushroom soup in heavy saucepan.  Melt cheese mixture on low heat; remove from stove and add 1/2 cup milk.  Stir until well blended.  In casserole, layer diced ham with potatoes.  Pour cheese mixture over ham and potato layers.  Add some shredded cheese and other 1/2 stick butter as a topping.  Bake for 45 minutes until casserole is bubbly.