Place mashed potatoes in a bowl. Beat eggs and add to potatoes. Add the sugar, salt, 1/3 stick margarine, sweetened condensed milk, vanilla, cinnamon, nutmeg, butter & sherry flavorings and beat on low speed until well blended and combined. Pour into buttered baking dish.
Mix remaining ingredients together except margarine. Pour the topping over potatoes, then pour the melted margarine over the topping. Bake 40 minutes in preheated 350 degree oven.