Sweet Potato Casserole with Pecan Topping

3 large sweet potatoes or yams (to yield 3 cups, cooked and mashed)
1/4-1/2 cup butter, melted
1/4-1/2 cup sugar
1/3 cup milk
1 tsp. vanilla
2 eggs

Topping:
1 cup light brown sugar
1 cup chopped pecans
1/3 cup flour
1/3 cup butter, melted

With vegetable peeler, remove skin and 1/4" slice from the ends of each sweet potato or yam.  Slice thinly, cover with water and boil until tender, about 20 minutes.  Whip with electric beaters and remove any "strings" that may collect on beaters.  Add butter and sugar to warm potatoes and continue mixing.  Add milk, vanilla and eggs.  Mix well.  Put in a buttered casserole dish (9x13).  Mix together the pecan topping ingredients and crumble on top of casserole.  Bake for 25-30 minutes at 350 degrees.  Serves 8-10.  (or more)