To prepare the sweet potatoes, place the sweet potatoes in a pot and cover them with water. Cover the pot and bring to a boil. Reduce heat to medium, and simmer until very tender. Remove the potatoes from their skins and place in a bowl. Add the powdered sugar, milk, beaten eggs, vanilla extract and 3 tablespoons melted butter and mash together.
To prepare the topping, in a separate bowl, combine the sugar, nutmeg, cinnamon, chopped pecans, flour, and 1/2 cup melted butter.
Preheat the oven to 350 degrees F.
Brush a 6x9 inch baking dish with melted butter. Place the potato mixture in the prepared baking dish and spread evenly.
Spread the topping evenly over the sweet potatoes.
Bake in the oven for 30-35 minutes or until the pecan topping is golden.
Serve it warm or cold.