Sweet Potato Casserole

4 cups cooked sweet potatoes (1 lg. can)
3/4 stick butter
1/2 cup flour
2 eggs
1 small can Pet Milk
1 cup sugar
1T vanilla
Mix above & place in dish
Topping:
1 cup brown sugar
1/2 cup flour
1/4 stick margarine
Mix and place over top of potatoes.  Bake in oven 350 degrees for 20 minutes.
Sprinkle with pecans if desired. 
*If using can potatoes, drain, cook and mash.