Preheat oven to 350 degrees F.

Scrub the sweet potatoes, then place them on a lined baking sheet. Bake the sweet potatoes for 45-90 minutes, or until the yams are very soft when poked with a fork. The baking time will depend on the size of the sweet potatoes. 

Let the sweet potatoes cool slightly, then cut the ends off and peel them.

Lightly grease a 9×13-inch baking pan with cooking spray. Place the peeled sweet potatoes in the pan, then dot with 1/4 cup of Smart Balance or other margarine or butter. Sprinkle with 1/4 cup brown sugar. Mash the sweet potatoes with a fork or potato masher, incorporating the Smart Balance and brown sugar at the same time. It doesn’t have to be completely smooth; rustic lumps are a nice touch. Set aside.

In a medium bowl, combine the brown sugar, flour, and cinnamon. Mix together, then add the Smart Balance and work in with your fingers or a pastry blender. Stir in the pecans.

Sprinkle the topping evenly over the yams. Bake uncovered at 350 degrees for 45 minutes or until topping is evenly browned. Serve immediately. Cool any leftovers, then cover and refrigerate.