Peel baked sweet potatoes and place into a large bowl. Add in brown sugar, vanilla, eggs, butter, and salt. Using a masher or hand mixer, stir together until completely smooth. (A few lumps are ok if you don't mind it lumpy!) Pour into a greased casserole dish and set aside.
In a medium-sized bowl, stir flour, brown sugar, granulated sugar, butter, and salt together until a crumbly texture is formed. Add in pecans and stir. Sprinkle topping over sweet potato base.
Bake for 1 hour, uncovered. (If you notice the streusel top becoming a little dark, cover with foil). Serve warm.
If you don't like streusel topping, feel free to replace with mini marshmallows--a classically American topping for Thanksgiving.