1. walljumb on the "plattform"
2. pull the mob and run to the other side and jump on the "latern"
3. wait until the mobs are near, then jump back
4. run to the chest and wait on the plattform until your ooc
5. jump down, open the chest and vanish / die (i usually use sprint while jumping down)
Video here
http://www.youtube.com/watch?v=SxJypQVQ4Gs