Preheat oven to 350°F.
Grease a 9 X 13 inch baking dish.
In a large bowl, mix potatoes and white sugar.
Stir in eggs.
Mix in vanilla, milk, and 1/2 cup melted butter.
Gradually stir in rum until well blended.
Transfer mixture into prepared baking dish.
In a medium bowl, mix brown sugar, pecans, flour, and 1/3 cup melted butter.
Sprinkle this mixture over the mashed sweet potato mixture.
Bake for 30 minutes.
Allow to sit at least 10 minutes before serving.
*The rum in this recipe can be adjusted according to taste. It also tastes good if you leave the rum out completely.*