Filling]
3 cups   cooked mashed sweet potatoes
1 cup     sugar
2           eggs
1/2 cup  butter
1 teasp  vanilla extract
 
Topping]
1/2 cup   light brown sugar
1/2 cup   chopped pecans
1/3 cup   flour
1/3 cup   butter
 

For the topping mix with fork the ingredients and sprinkle crumbs on top of casserole.  Bake at 350 degrees for 20 to 25 minutes.  

[This recipe from family in Wesson, Mississippi.]