Lembas

Regenerate target creature. You gain life equal to that creature's toughness.
"Eat little at a time, and only at need. For these things are given to serve you when all else fails. The cakes will keep sweet for many many days, if they are unbroken and left in their leaf-wrappings, as we have brought them. One will keep a traveler on his feet for a day of long labour, even if he be one of the tall men of Minas Tirith."