Machine turned off by dog during bios upgrade

Satellite L755, started bios upgrade, battery dead, so plugged it in, went to the kitchen, leaving the bios upgrade running. My dog apparently pulled the power cord apart while chasing a fly, I didn't notice, and the laptop shut down. Now nothing works, obviously.

Luckily, lots of backups, so I have all my data, but how do I restore the bios at this point?

Thanks.