Butter

Butter is one of the ingredients Princess Peach used to bake a cake for Gourmet Guy in Paper Mario. After the cake is finished Gourmet Guy will tell Peach where the next Star Spirit is being held, and Twink will relay that information to Mario.

Butter is based upon the real-world substance of the same name.

It's item description: The best butter available. It looks freshly churned.