i was wondering if it possible to have the extra mounted HDD configured as iSCSI with IP adress to connect to as share?
No, ESXi doesn't work as an iSCSI target. What you could do though is to create a new VM (with iSCSI target software) with a virtual disk on the second HDD. It may not make sense however to map this iSCSI target to the host itself (hen-egg issue).
André