Combine sweetened condensed milk with lime juice in a small bowl; beat or whisk until smooth.
Remove only the green portion of the lime peel (or zest) using a microplane grater. The white portion of the peel underneath the green is bitter, so be careful to avoid it.
If you like a little extra "zing", 1/2 packet of True Lime flavoring may be added, but this is entirely optional.
Whisk the lime peel (and True Lime, if using) into the milk and lime juice mixture.
Pour into the graham pie crust and spread with Cool Whip topping.
Chill for several hours or until mixture sets.
The top may be decorated with curls of lime zest, if desired.
Submitted by: CM
