For filling, in a large pot combine potatoes with enogh cold water to cover, over high heat bring water to a boil. Reduce heat to medium; simmer until potatoes are tender, 30 minutes. Drain and mash until smooth. Let stand until cooled slightly, 15 minutes. Preheat oven to 350. Butter 2-qt baking dish. Combine potatoes with the rest og the filling ingredients. Spread mixture in baking dish. For topping, in a large bowl combine pecans sugar and flour, stir in butter until mixture is combined. Sprinkle over potato mixture. Bake until top is brown and center is set, 40-45 minutes.