Preheat oven to 350 degrees.
Prick the skin of the potatoes in several places, and place on baking sheet. Bake until tender.
Remove the potatoes from the oven, let cool about ten minutes. Slice lengthwise, remove the pulp, and put in large mixing bowl. Mash the potatoes with milk and butter, to desired consistency. Add spices to taste.
Grease a large casserole dish, and add potatoes.
While the potatoes are baking, peel, core and slice apples. Melt butter in large skillet, add sugar, cinnamon and apples and cook over low heat until apples are tender.
Spread the apples over the top of the sweet potatoes, and place under heated broiler until brown and bubbly.