I presently test various network booting operations on a variety of virtualization platforms. These all leverage the same UEFI firmware support, based on Intel's EDK II project. That has supported the ability to do HTTP Boot for quite some time (see section 24.7 of the UEFI specification, e.g. https://uefi.org/sites/default/files/resources/UEFI Spec 2_7_B.pdf), but this is not supported in Parallels. (It works fine in VMware Fusion, QEMU, and other virtualization platforms.) Could you add this to the UEFI firmware to support this?