Preheat oven to 350ºF.
Combine sweet potato, 1/2 cup flour, eggs, 1/2 cup butter, sugar and vanilla in a large mixing bowl. Spread the mixture into a casserole dish.
For the crust whisk together the brown sugar and flour.
Cut in the butter in small chunks using your hands or a pastry knife to combine until it looks like the consistency of coarse meal.
Spread the mixture on top and bake for 30 minutes.