1. Peel the sweet potatoes and cut them in half. Place them in a pot and cover with cold water. Bring to a boil over high heat and simmer until the potatoes are tender when pricked with a fork, about 30 minutes depending on the size of the potatoes. Drain.
2. Meanwhile, toast the pecans in a nonstick skillet for 2-4 minutes or in a toaster oven and set aside.
3. Mash the potatoes and brown sugar with a potato masher or fork, or use a food mill.
4. Adjust the cinnamon to taste.
5. Transfer to a serving dish and top with the toasted pecans.