As you progress through your Paper Mario: The Thousand-Year Door campaign, you'll want to make a habit of visiting the Trouble Center at the end of each chapter. The Trouble Center is located at the far east end of Rogueport, beyond Professor Frankly's house. Here, you can accept Troubles, or side quests. This feature becomes available after you've arrived in Petal Meadows. On the downside, you'll only be able to take on one side quest/Trouble at a time, and canceling one side quest for another costs 30 Coins. "Heartful Cake recipe..." is one of the many requests you can sign up for, but is it worth the effort?