Recipe(tried): Sweet Potato Crunch - Dana, does this sound like what you are looking for?

Dana, my brother requests this every Thanksgiving. It doesn't have walnuts in the topping but you could surely add some.

SWEET POTATO CRUNCH

3 cups mashed sweet potatoes*
1 cup white sugar
2 sticks (1 cup) margarine or butter, softened, divided use
2 beaten eggs
1 cup milk*
2 teaspoons sherry (optional; or use 2 Tablespoons)
1 teaspoon vanilla
1 cup brown sugar
1/3 cup self-rising flour
1 cup chopped pecans

Preheat oven to 300 degrees F. to 350 degrees F.

Beat together potatoes, sugar, 1 stick margarine, eggs, milk, sherry and vanilla. Pour into casserole dish.

Mix brown sugar, remaining stick of margarine, flour and pecans. Crumble over casserole.

Bake for 30-35 minutes.

*If using canned potatoes, reduce milk to 3/4 cup. You can more or less drain canned potatoes. You may use evaporated milk.