Preheat your oven to 350 degrees Fahrenheit.
Prick the sweet potatoes with a fork and bake them for about 1 hour and 15 minutes, or until they are tender.
After the sweet potatoes have cooled a bit, scoop the flesh into a large mixing bowl.
Use an electric mixer to beat them until smooth and creamy.
Add eggs, granulated sugar, 1/2 cup of melted butter, milk, vanilla extract, and salt to the potatoes.
Mix everything well until fully combined.
Pour the sweet potato mixture into a greased baking dish, spreading it out evenly.
In a separate bowl, combine the brown sugar, flour, chopped pecans, and the remaining melted butter.
Sprinkle this topping evenly over the sweet potato mixture.
Bake the soufflé for 25 to 30 minutes.
If the top starts browning too quickly, cover it with foil during baking.