Thinly slice broiler potatoes (about 4), and layer in a 9x13" pan with sliced onions, mushrooms and ham.  Sprinkle with Parmesan grated cheese and a handful of grated cheeses (of your choice).  Repeat layers 2 more times.

Mix 1 cup each milk and Miracle Whip until smooth and pour over potato mixture.  Sprinkle with additional shredded cheese to cover top.

Bake covered in 450 degree oven for 50 min. or until potatoes are tender.  Let stand 5 min. before serving.