I know you're memeing but mass-migration of Iranians into the EU would more likely turn into a continent-wide gang war a la the Crips and Bloods between the Shia Iranians and Sunni Turks/Pakis/etc, instead of them actually coordinating to establish a caliphate.Let me tell you exactly how this will play out:
Step 1 - The US starts bombing Iran.
Step 2 - Iran conquers Europe by sending 50 million refugees which then just take over.
Step 3 - London is renamed New Tehran, Britain becomes the central district of the new Islamic Caliphate.
Step 4 - The EU is officially renamed the "Islamic Union". Hungary and Poland are promptly expelled and pacified by force.
Step 5 - The US marches into Tehran largely unoposed and declares victory over Iran.