The Fortified Delicacy is a mollusk shell, sold as a treasure in Pikmin 2. To get it, you'll need to destroy the rock formation on top of the Shower Room, and then eliminate any Yellow Wollywogs that stand in your way. Next, you'll need White Pikmin to dig up the treasure, near one of the corners in the tiled area. Let them dig it up and transport it to the ship.