Preheat oven to 325°F.
In a medium pot, cover sweet potatoes in water and cook over medium-high heat until tender; drain and mash.
In a large bowl, mix together the mashed potatoes, sugar, eggs, salt, butter, milk, and vanilla extract, until smooth. Poor in a greased 9×13" baking dish.
Mix the brown sugar and flour in a medium bowl and cut in the butter until the mixture is coarse. Stir in pecans, and sprinkle the mixture over your sweet potato mixture.
Bake for 30 minutes or until the top is lightly brown