if you get the max level for cooking u can make ambrosia "drink of the gods" you will need two ingredients, deathfish from graveyard pond and a life fruit which is somewhere or you can find a rare seed & plant it and hope its the right plant.. then use those in making the recipe, then if you drink it you grow younger, but if a ghost drinks it they become alive again.
hope this helps.
you don't grow younger by eating ambrosia, it just reset the days you have left until the next age to 0