Preheat your oven to 400.
Grease baking dish with butter and set aside.
Pierce sweet potatoes with a fork to allow steam to escape.
Place on a baking sheet and bake for 45 to 60 minutes, until a fork can be easily inserted into the center.
Reduce oven temperature to 350.
Slit skin and scrape flesh into a large mixing bowl.
Add sugar, salt, vanilla, eggs and butter. Beat until fluffy and blended.
Transfer to prepared baking dish and set aside.
Combine topping ingredients in a mixing bowl.
Using a pastry cutter or fork press firmly to form crumbly topping.
Sprinkle topping evenly onto top of sweet potato mixture.
Bake for 30-40 minutes, until potatoes are hot and topping is lightly browned.
Allow to set for 15 minutes before serving.