Peel sweet potatoes and cut them into about 1-inch chunks. Place in a medium pot and cover with water. Boil potatoes until they are soft and tender and easily pierced by a fork, about 20-30 minutes. Drain and mash.
Preheat oven to 350 F. Combine the first seven ingredients (all but the topping) in a bowl, and stir well. Alternately, mix with an electric mixer (no need to mash potatoes first). Spoon sweet potato mixture into a 2-quart baking dish.
Combine 1/2 cup brown sugar and flour for the topping in a bowl. Cut in 2 tablespoons chilled butter with a pastry blender or 2 knives until mixture is crumbly. Stir in pecans. Alternately, take the lazy route and mix the topping in your blender or food processor. Sprinkle topping over sweet potato mixture.
Bake for 30 minutes or until topping is bubbling at the edges.
Source: slightly adapted from Cooking Light Five Star Recipes, the Best of 10 Years