Cook sweet potatoes in boiling water to cover 30-45 minutes or until tender. Let cool to touch; peel and mash.

Combine potato, brown sugar, eggs, vanilla, half & half (or milk) and butter; beat at medium speed with an electric mixer until smooth. Spoon into greased 13×9 baking dish.

Topping:
Combine brown sugar and flour; cut in butter with a pastry blender until mixture is crumbly. Stir in pecans.

Bake, uncovered, at 350 degrees for 30-35 minutes or until lightly browned and bubbly around edges.