I'm aware a few of us have this issue - where it takes a very long time to boot and longer when you have more memory.  I've just seen something that I thought I'd share.   Basically, while watching HTOP, starting a VM that isn't already started with dedicated (not shared / ballooned) 32GB RAM, the VIRT Ram is set straight away to 32GB, but the RES RAM slowly counts up to 32GB.  Once the RES RAM reaches 32GB, suddenly the TIANOCORE BIOS is displayed and then we're good to get booting.