Souffle: Preheat the oven to 400 degrees F. Lightly grease an 8-inch square baking dish.
In a large bowl, combine the sweet potatoes, sugar, eggs, milk, butter, vanilla, and salt. Pour the mixture into the prepared baking dish.
Topping: Combine the brown sugar, butter, flour, and pecans in a separate bowl. Crumble the topping over the sweet potato mixture.
Bake for 20 to 25 minutes, until the topping is golden brown. Serve hot.