Buffett Potatoes

8 large potatoes
1/2 cup butter melted
3 oz. cream cheese
1/2 cup sour cream
1/4 cup milk
1 1/2 teaspoon salt
1/2 teaspoon pepper
1 medium onion chopped
12 large mushrooms, sliced or diced

Peel, dice and boil potatoes till done, then drain.  Cream potatoes with cream cheese, sour cream, milk, salt and pepper.
In a separate pan saute' mushrooms and onion in the butter.
In a casserole dish layer half of the potatoes, then the mush room mix and top with rest of potatoes.