Peel the mango. Cut the flesh from the stone and dice it. Place in a zip-lock bag, close it (be careful to keep the air out) and freeze for at least 4 hours.
Take the bag out of the freezer and allow to thaw for about 20 minutes at room temperature.
Put slightly thawed mango pieces into a tall bowl (or the bowl of your blender), add powdered sugar (if using) and puree the mango into a creamy sorbet using a hand-held blender (or simply blend in your blender).