H e never asked to become a rosh yeshivah — in fact it was the furthest thing from his mind when just a teenager himself he began to say a shiur in public. So how did Rav Shneor Potash wind up at the helm of Yeshivas Chachmei Yerushalayim a burgeoning mosad where the third siyum haShas of the zeman is being celebrated by a bochur next week?