Butter

Butter is a beta item from The Legend of Zelda: The Minish Cap. It is unknown where it can be obtained, if at all, in game (without cheating). According to the game's text, it was to be obtained by Link turning Lon Lon Milk into butter by an unknown method. It restores hearts and is kept in an Empty Bottle. It can be obtained through cheating.

Code
The following is a Codebreaker code for the butter. It fills all of Link's Empty Bottles with butter.
 * 82002B38 5555
 * 82002AF6 2121
 * 82002AF8 2121