Seeking Legendary Book!

Seeking Legendary Book! is the eighteenth Trouble Center mission in Paper Mario: The Thousand-Year Door, initiated by Zess T. It is first available after clearing Chapter 4.

Mission
Mario must visit Zess T. in her house in Rogueport, where she tells him of a legendary cookbook hidden in Creepy Steeple. If Mario had not obtained the cookbook during his first visit to the Creepy Steeple, he must travel to Twilight Town, make his way through the Twilight Trail to the steeple, and use the Tube Mario ability to enter a secret room, where he uncovers the cookbook in one of the chests. Mario must then return to Rogueport and give the cookbook to Zess T., who cooks him a Honey Shroom as a reward for solving her trouble. From then on, Zess T. can mix up to two ingredients instead of just one.

In-game description

 * "I want you to find the legendary cookbook for me! It's in a pretty scary place, so there's no way an old gal like me could get it alone! Please come to my house in Rogueport Square for details!"