Combine sweet potato, salt and the cinnamon in a medium saucepan with just enough water to cover. Boil, uncovered, stirring occasionally, until potato is tender, about 20 minutes. Drain. Discard cinnamon stick.
Return potato to pan. Add 1½ tbsp maple syrup and all the butter. Mash. Serve drizzled with the remaining maple syrup.
Pure maple syrup has a smoother, more subtle flavour than imitation syrups. Cheap versions are usually made from corn syrup with a little pure maple syrup added. Maple syrup will go further if you heat it.