Pull off any loose outer leaves of the sprouts and trim the stems; cut an X in the bottom of each to allow for even cooking of core and leaves.
Put the sprouts in a saucepan with the butter and cider or juice, bring to a boil, and simmer, covered, for 5 minutes.
Meanwhile, peel and core the pears.
Cut them into chunks roughly the size of the sprouts.
Add them to the saucepan with a pinch of cinnamon and continue simmering another 5 to 7 minutes, until the sprouts and pears are both tender.
Watch that the cider doesn't evaporate; if necessary, add a little more.