Put peeled, sliced sweet potatoes in a large pot with water to cover.
Cook over medium high heat until tender; drain and mash in the pot with a hand blender
In the same pot, mix together the sweet potatoes, white sugar, beaten eggs, salt, butter, milk and vanilla extract. Mix until smooth. Transfer to a 9x13 inch baking dish. If preparing the day before - you would cover and refrigerate at this time
For Pecan Topping:
In medium bowl, mix the brown sugar and flour.
Use a fork or a pastry cutter to cut in the softened butter until the mixture is coarse. Stir in the chopped pecans.
Sprinkle the mixture over the sweet potato mixture.
Bake in the preheated oven 30 minutes, or until the topping is lightly brown.