2Place ham in a 2 quart casserole dish and top with corn. Heat in preheated oven 10 minutes. Remove and top with mashed potatoes. Heat in oven for 20 more minutes, then remove.
3Turn oven to "broil" setting. Dot potatoes with butter or margarine, then place pie under broiler just until golden brown on top, about 3 minutes. Serve immediately.