My mother, Kathy, made this recipe every Thanksgiving. I learned to love it!  Being the short order cook I am in my house, I add Pecan topping to half of the casserole and Marshmallows on top on the other half. 

Ingredients:
3 Sweet Potatoes
½ tsp salt
1 cup sugar
½ cup milk
1/3 cup margarine
1 tsp vanilla

Directions:
Cook Sweet potatoes whole in a large pot for about 25 minutes. Once a fork can easily go through the middle of the potato, remove from heat and pan and the let cool for about 5 minutes. Peel the skin off the potatoes. Caution the potatoes are still hot. Next, in a large mixing bowl mash the potatoes finely and add butter and milk, salt and mix well. Then add sugar and vanilla and mix well.
Add these ingredients to a baking dish. Preheat oven to 350 * F

Topping Mixture:
1 cup Brown Sugar
1/3 cup self- rising flour
1/3 cup melted butter
2 cups whole pecans

Final Step:
Mix all ingredients well. Add to the top of the sweet potato mixture.
Place in the preheated oven and bake for 30-35minutes.