How do you fix a broken valve cover bolt on a Chevy 1500 with a 5.3?

Remove the broken bolt and replace it with a new one. There are several ways to remove that broken bolt. You can remove the valve cover and weld a nut to what is left of the bolt, wait for it to cool off then unthread the broken bolt. You can also drill out the center of the broken bolt and use an easy-out. You can also drill into the broken bolt with a left handed drill bit, sometimes the drill bit will catch and spin out the broken piece. I would go with the first suggestion.