Add this into your triggers.scp file:

SECTION TRG 150
{Elvish Pie
EMT Mmm..  That tastes very good.
MSG You gain 5 health
HEA 5
REMOVE
}

If you want the pie to heal more damage, just edit the HEA # above to whatever you want.
And add this into your ITEMS.scp file:

SECTION ITEM 80004
{
NAME Elvish Pie
ID 1041
TYPE 14
TRIGGER 150
DECAY
VALUE 150
RESTOCK 10
GOOD 5
ALIGNMENT 0
MODIFY1 0
MODIFY2 0
MODIFY3 0
MODIFY4 0
MODIFY5 0
FAME 0
}
