Preheat oven to 375 degrees. Spray a medium-size casserole dish with nonstick spray.
For the crust: Combine brown sugar, flour, nuts and butter in mixing bowl. Chill in the fridge until ready to use.
Combine sweet potatoes, sugar, salt, vanilla, eggs and butter in a large mixing bowl in the order listed. Beat thoroughly with a hand mixer for about 3-4 minutes.
Pour mixture into the baking dish. Bake for 25 minutes.
Sprinkle the surface of the sweet potato mixture evenly with the crust mixture and return to oven for 10-20 minutes or until crumble is browned.
