Oblivion:S'jirra's Famous Potato Bread
The ingredient S'jirra's Famous Potato Bread can only be obtained from S'jirra at Faregyl Inn, and only after you have completed the quest The Potato Snatcher. In reward for completing the quest, you will receive one to five loaves of Potato Bread (depending upon your level). Additional loaves can subsequently be purchased from her through dialogue for 25 gold per loaf.
It is considered to be food, meaning NPCs may eat any samples you leave out of your hand. The bread cannot be duplicated in the Arch-Mage's Enchanted Chest.