From the Super Mario Wiki
Inky Sauce is a healing item found in the game Paper Mario: The Thousand-Year Door and Super Paper Mario. The item can be created using various recipes, and is described as "foul juice", possibly because of its bad taste or its use in a Poison Mushrooms recipe.
In Paper Mario: The Thousand-Year Door, Inky Sauce heals thirty FP; in Super Paper Mario, it restores three HP, and is sometimes dropped by Bloopers.
Names in other languages
||black watery soup