Need overworld enderman farm suggestions

[LannyRipple]

Hello. I'm looking to build a farm that will also capture ender pearls. My concern is the enderman stealing part of the farm.
Played on a server and one of the gang (Hi ExpHP!) had a brilliant farm but I never looked inside to see the workings. Does
anyone have any suggestions? (I know you need them to drop 40+ blocks for insta-kill. Mostly wondering how to stop them
from pulling the farm apart?)

[dawnraider]

Just build it out of blocks endermen can't pick up. Almost all, or maybe even all, man-made blocks cannot be picked up afaik.