Q. What on-premises components are required when using the Azure Site Recovery protection for VMware?
A. The protection of VMware VMs is enabled through an in-OS agent that sits between the the file system and the volume manager and acts as a volume filter driver. As writes occur from the file system down to the volume manager the write is also sent to the provisioning server which is then sent to a master target component which duplicates the writes to its own mounted virtual disk, one for each protected disk.
For the components required on-premises is an ASR configuration server instance which is a VM that also acts as the provisioning server to act as the target for the initial writes. This is the only piece required on-premises. The master target component in Azure is now transparent and is just part of the ASR service and not an instance you have to manage.