The Rescue of Old Nell is one of the first quests you can complete on your Adventure. After you rescue her the owners reveal they want to cook her for a feast, and provide you with a couple of her haunches to take with you (as well a magic item).
The haunch is just the same as a haunch you can buy from butchers in towns but is specifically referred to as a haunch of Old Nell.
The main thing is to make sure you use the items and don't sell them once you get them.