A Gradual Syrup is an item found in Paper Mario: The Thousand-Year Door and can be purchased at the Deepdown Depot for fifteen coins. It heals 2 FP per turn for ten turns.
Gradual Syrup is the Syrup counterpart to the Slow Shroom. Oddly, however, they cannot be swapped using a Point Swap and one or the other with Zess T. after retrieving the Cookbook.
In Super Paper Mario, it can be made by Dyllis of Flopside who can make it out of a Long-Last Shake and a Peachy Peach. Her version of the item gradually restores HP (20 HP total).